Hammond Organs

I've been a Hammond Organ enthusiast for quite a few years now.
Here you can see some of the organs I've owned, and various other notes I've collected over the years.
Various Hammonds and Leslies I used to own, or maybe still do.

You can see a page of much older stuff I've owned or seen here, including the 'chopped' organs I tried to make in the early 1990s.

Hammond A101
A 1962 A101; basically an A100 in an 'art deco' cabinet. Imported from the US.

Hammond C3
A 1965 C3, whose cabinet I refinished (see Sevice Notes). It's one of the first red-cap tone gen models. I've since added a Trek II reverb and a Trek II pedal unit (these are both really nice addons).

Photos lid open, lid closed, other side.

Hammond A100
A 1961 A100. When I bought it, it was in 'living room' condition. But I was young, and I moved it around a great deal, including up and down many stairs, and the cabinet became a bit trashed :( Sold to a man in Italy.

Hammond M3
I bought an M3, in really excellent condition (though badly sun faded) to go with my 145. I replaced the preamp caps and re-felted the manauls, now it plays wonderfully. It also came with the "optional extra" reverb unit, which is very nice to have!

Photos front, tabs, back.

Leslie 145 #1
My first ever Leslie - a 145 from 1973 which came from a living room. Sadly I was young and gigged it quite a bit, fool me, but it's still in pretty good condition. Currently wired up to my M3.

Photos front and back.

Hammond BC
A Hammond BC I acquired from a church. It had been sitting in there for 70 years, and was in dire need of an overhaul (see "Service Notes"). Sadly the bench had gone missing at some point in the past. Sold to a man in Germany.

Leslie 251 #1
A Leslie 251, probably built 1967. I refinished the cabinet. Since sold to a man in England.

Leslie 145 #2
A fairly beaten up 145 I bought quite cheaply, and refinished. It came out in a lovely deep brown colour. Since been sold to a man in Italy.

Leslie 251 #2
A 251 I bought which had been heavily gigged. The cabinet was in pretty dire condition, so I refinished it. Since been sold to a man in Finland.

Leslie 145 #3
A 1974 Leslie 145 straight from a living room, never moved before I acquired it, in immaculate condition. The back had never been removed - when I did so to give it all an overhaul, I found the original warraunty card inside.


Leslie 251 #3
Another 251 I acquired which had been heavily gigged AND at some point painted red and varnished. The cabinet was in really dire condition, so I refinished it - shame I have no "before" photos! This time I used Danish Tung Oil, which went OK, though possibly it needs another coat or two. Since sold to a man in Finland.

Leslie 145 #4
Another pretty standard 145 in immaculate condition except for the top, which has a terrible unremovable water stain on it! Such a shame.

Leslie 145 #5
This later 145 from 1976 looks to have a much darker wood finish on it than any others I've seen. Perhaps these later models were.

Here are some notes on some of the more daunting servicing jobs I've done, for any who might be contemplating them.
Most of the parts listed below can be bought as kits from Goff Prof, Tonewheel General or Trek II.

Replacing 100 Vibrato line capacitors
I installed a replacement capacitor kit in my 1965 wax cap A100. This was a pretty straightforward job.

The leads on the caps would have been long enough to completely remove the old ones and replace, but instead I snipped out the old components and soldered the new ones on the old leads (see photo of old caps). This was made very simple by bending the old cut lead up into a little hook, then bending the new cap leads into a matching hook, and hanging the new caps (and resistors) in place for soldering. The whole job took me maybe 30mins.

Overall, the chorus sound (sorry, I never use vibrato) was certainly deeper and more prominent, enough that C3 now seems too heavy, and C1 adds more than just 'brightness'.

A100 A0-28 electrolytic capacitors
I bought a replacement preamp capacitor kit (from Tonewheel General) for my 1965 A100. This consists of two can capacitors, three ordinary electrolytics and some instructions. Replacing them all was fairly straightforward (the pictures in the instructions helped enormously) - I didn't even remove the whole preamp (as was advised), but left the wires in place and just slid it out from where it's hung and propped it up. This gave me enough access to do all the soldering required.

I measured the old caps afterwards, and they had all drifted by between 25% and 50%, mostly downwards.

I would say that this job is only suitable for someone with fair confidence with a soldering iron. A 'solder sucker' (to remove the old solder on the caps) was also enormously useful.

A100 manual felts
Replacement up and down stop felts can be bought from Trek II.

This was a straightforward, if fairly long job. I removed the manual bolts and music rack top, and removed the bolts holding the two manuals together to give myself more leeway. Removed the screws from the upper manual front strip and peeled it off (it was stiff, but with slow pressure the glue did give way - pull too hard and the strip would bend). Under the keys was filthy (dust), but I didn't pull them all off to clean up inside. There was certainly enough room to get at the downstop felt under the keys with out removing them.

I peeled off the old felts, both of which were very hard, cleaned up the glue that was left with a soapy cloth (I decided I didn't need to remove it all), and then carefully stuck on the new felts, doing a few cm at a time and keeping them tight to the edges. I then reattached the front strip (without any glue - why did Hammond bother?).

After the top manual, I put back the bolts joining the two manuals, then raised the pair up on a couple of bits of wood to get at the lower manual front strip, and repeated the whole process.

Although there may be no difference in sound, the feel of the keys is now much smoother. This is absolutely a job worth doing - the difference is astonishing.

A100 buss bar cleaning
Inside each manual there are 9 'buss bars' running the length of the keyboard. These can get dirty over time (though it's a sealed unit so shouldn't really) and can be cleaned.

I tipped the organ (A100) up on it's side (preset side up!) (slide in some paper between the righthand manual ends and woodwork to avoid scratches), undid all the manual bolts (maybe should have done this before tipping up the organ?) and top cover screws, and eased out the manuals enough to remove the two end plates.

I then loosened the screws on the bakelight (sp?) covers, pushed them out of the way, and ONE AT A TIME removed and cleaned and replaced each bar. Make sure none of the presets are pushed down or you'll break the buss bar when you try and get it out.

I cleaned them with a lint free cloth ("pec pad") with some de-oxit sprayed on, by drawing the cloth evenly down the bar in one go, then repeated the process with some bus bar lube.

I then carefully fed them back in again, replaced the plates, tipped the organ upright and screwed back the manuals. This was a very straightforward job, though in truth it made very little difference to the playing action. I suspect it is only worth doing if you have a large number of dirty contacts (tones not being heard unless you wiggle the keys about).

BC manual felts
This is a more involved job than on a later organ (A100/C3/B3) since the front strips are fixed in place, rather than screwd on.

Before anyone attempts this, make sure you have the right tools - I used a flathead screwdriver, a socket set (with both sockets and screwdriver attachments), pliers and various other bits. This is a much more fiddly job than on the later organs.

I removed the music rack completely (remove a pin from the levers coming from the chorus 'drawbar' to release it, undo the four bolts on the top and slide it out), and the four long bolts from underneath the manuals and the two bolts used to join the two manuals together. And the two screws holding the lower manual to the front rail.

I lifted the manuals together enough so that the lower manual was free of the front rail. I then removed all the screws from underneath along the front, and the two bolts at each end. The front strip could then be prised off; it was very stiff, but did come eventually. The upstop felt is on this strip, and I peeled it off, cleaned up the metal and stuck on the new one (trek II). The downstop felt is attached to a strip of metal which will be loose once the front strip is removed. Again, I removed the old strip, cleaned up the metal and stuck on the new one.

Now comes the job of putting it back together again. This is very fiddly. I put back the metal strip with the downstop felt on it, then slid the front strip back in place by starting at the presets end and pushing down the keys as i went along to the high end. Next the bolts have to be replaced - do this before replacing the large bolts on each end. The problem here is with the first few bolts; they need to go through the front strip from underneath and screw into the loose metal strip on which the downstop felt is stuck. I used a narrow screwdriver to push through a screw hole towards the righthand end to align all the holes up, and then loosely fiddled a bolt into place. I then repeated this near the middle, and then near the left end, and then put in all the bolts loosely, before going along tightening them all up. The far righthand bolt has a spacer which it would go through inside - I could find no way to hold this in place while putting the bolt in, so left it out. Finally I put back the large end bolts and dropped the manuals down again.

For the upper manual, I followed exactly the same procedure; I propped up the manual as far as I could (you need to get it pretty high in order to get at the nuts for the large bolts on each end of the manual), and had to use a socket wrench with a screwdriver head to get at the bolts.

In all, the job took maybe 3 hours. Once complete, the biggest difference I noticed was that the keys have a smaller travel range than before; more so than when I refelted by A100. There's no question that the playing action is improved, as it was with the A100, and this was definitely worth the effort. I could have replaced the front strip bolts with metal screws to make it easier next time, but I didn't, reckoning that it ought to be many many years before I would need to do this again.

A couple of photos of the raise manuals: one and two. Excuse the mess.

BC tone generator recap
I bought a new capacitor kit from Goff Prof for this, which includes all the capacitors on the tone gen, plus a set of filters to add to old organs.

I removed the four main keyboard bolts and tipped up the manuals, proping them up with bits of wood. This gave me a gap of about 10cm to get at the top of the tone generator.

Removing the felt showed me all the capacitors. I did the replacement in small numbers (blocks of 3 or five), cutting the leads on the old capcitors, then shaping the leads on the new ones and hooking them over the old leads, before soldering them in place (I used a 40W iron - goffs suggestion of a 100W one seemed excessive!). The reason for doing them in small blocks was that this is a very fiddly job, and taking breaks was important. For instance, once each new cap was in place, the extra wire had to be snipped off while holding it with a pair of narrow pliers to avoid them dropping into the tone gen ...

The 37 main caps were fine; replacing the 7 centre one was an even more fiddly job, and two of them (covered by the oil cups) were hell. I also didn't put in the RC filters, since on a BC there is no access at all to the back of the tone gen - I would have either had to remove the manauls completely, or remove the chorus gen, both of which are major tasks.

I tested the tone gen with the manuals still raised (pull out 8' db, play every note on a manual, pull 1' db and play the rest), then lowered them back down and did up the bolts.

Then I lifted the manuals again and replaced the green felt I had forgotten about (duh).

The old caps were a long way from their original values; most of the 0.1uF were now 0.5uF (they were 70 years old). However, just how much difference it made was rather hard to judge.

A couple of photos of the raised manuals: one and two. Excuse the mess.

Leslie 145 cabinet refinish
I acquired a 145 for not very much money, which was immaculate inside, but a bit beat up on the outside. Internally, I replaced the electrolytic caps, valves, upper rotor belt and lower rotor gromet, and cleaned out all the dust. Then I started on the case:
  1. Empty the cabinet - I removed the amp & lower rotor, but left the motors and horns in place, though I covered the horns with old pillow cases.
  2. Strip off the lacquer - I went to homebase and bought a tin of 'Nitromors Varish & Lacquer Remover'. Using this, the lacquer came off pretty easily, although it's a long and tedious job. Turning the leslie over so the surface to be stripped is on the top, you need to slosh on the nitromors liberally over an area, then wait a few mins for it to start to blister, then slosh on yet more and wait 20mins. Then scrape it all off - I used a tool for putting on plaster, which worked fine, dragging it along the grain of the wood. For the louves & fiddlye bits, I used cheap toothbrushes. It's important to not let the stuff dry out, or you can't scrape it off. This is a very messy job. Keep the windows open, and cover the floor. Here's a photo of a small test area I tried out on the top first, and later on.
  3. Sand out the scratches - I used coarse (100 grade) sandpaper and a block to sand over the whole surface (and back panels) to remove the scratches. This produced a lot of dust ... but was remarkably successful. I found Homebase also sold 'flexible' sandpaper with a rubber back which I used on the fiddly bits.
  4. Fill in the more major dents - I bought a light coloured wood filler (Cuprinol Fine Wood Filler), and applied it highly liberally to the various deeper dents and nicks, making little attempt to shape it corectly at this point.
  5. Sand it down again - I went over the whole case again with a fine (240 grade) sandpaper. At this point I sanded down the wood filler to shape (filler really works, btw, texture wise it blended seemlessly with the wood). I also sanded round the front edges. See photo - the wood filler can be seen along the edges.
  6. Re-stain the wood - There's much discussion in the hamtech archives about wood stains, but in the end I just bought a tin of Colron American Walnut Wood Dye. I rubbed it on with a cloth; it went on very easily, though it's really important to push hard in order for it to evenly stain into the wood. See photo. After much consideration, I put on a second coat. This did even up the finish some - see photo.
  7. Lacquer the cabinet - Again, there's much discussion in the hamtech archives on the final finish, with people opting for polyurathane (water proof, bit ugly), shellac (beautiful, but labour intensive), tung oil (more matt than shine I believe) and lacquer (requires spraying). Given the leslie seemed to have lacquer on originally, I thought I'd go with that, and went to Homebase and bought a tin of paint on lacquer (rather than spray on) (Colron Interior Lacquer (satin)). I tried it out on the upper horn back panel, and that looked pretty good, so I went over the whole cabinet; 2 coats, then light sanding and a 3rd coat, see photo.
  8. Buff the finish - I bought a tin of Colron Finishing Wax and applied 3 coats with fine wire wool, then a final coat with a cloth. I got through a lot of wire wool (200g packet).
  9. Apply the decal - I ordered a Leslie decal from Tonewheel General and put that on.
  10. Final result - So here's the final result; back and front.
  11. Things I Have Learnt - ah, the wonder of hindsight.
    • Remove all the old lacquer! Obvious thing to say, but this was much harder to remove from the louvres than anywhere else (as someone else has said), and although I thought I'd got it all out, once stained I realised that I had missed some bits.
    • Wrong colour filler - I bought a light coloured filler, assuming it would stain dark with everything else - initially it did, but once the stain has dried, the filler became light again, and so it's now obvious where I used it. Use a dark filler!
    • Paint on the lacquer really thinly, otherwise it runs a little and forms little drops. And when sanding off the 2nd coat, sand really lightly or you'll take it all off again ... This was the only part of the process that I think I got really wrong (should have used gloss, not satin also), and if I did it again I'd look for a spray lacquer ...
    • Not really a mistake, but I ought to put some more buff on it ...

In all I think it was a success, even with the wrong coloured filler and lacquer issues. Certainly next time I'd be able to do a better job! It was a fair amount of work, but then I was in no hurry. It's made me consider doing the BC cabinet, but that would be a lot more work - more area to cover, and a lot of very fiddly bits, and I'd probably have to get the manuals out, which would be so much grief ...
Leslie 251 cabinet refinish
I bought a 1967 Leslie 251 in fair physical condition, though possibly it had been varnished at some point. Since I was made redundant and had time on my hands, I decided to refinish the case anyway - this was going to be my primary 'living room' Leslie, and previous experience with a 145 made me Confident.
  1. Empty the cabinet - I removed the amp, lower speaker & rotor, horns & driver and reverb speakers. I left the motors in place. With the 145 I initially left the horns & rotors in place, but this caused more grief than it was worth, so I pulled everything out this time. I also sealed off the louvres with masking tape to stop the paint stripper dripping inside ...
  2. Strip off the lacquer - 'Nitromors Varish & Lacquer Remover' as per the 145; a long and messy process. It was harder to remove than on the 145, and also unlike the 145 I found that the brown on the louvres was in fact painted on, and also flaked off; this was entirely unexpected - why did Leslie do this on some cabinets?
  3. Sand down the cabinet - Just coarse (100 grain), then fine (240 grain) sandpaper and much work. I put more effort into sanding out the lourves this time also. The louvres were left with their original whate base coat on.
  4. Deal with the louvres - After some advice, I took some dark wood filler (Ronseal Dark Walnut Wood Filler) and carefully applied it to the louvres with my fingers, then sanded it down with fine (240 grain) sandpaper, see here.
  5. Stain - First I wiped the sanded cabinet down with a cloth damped in white spirit, then I used an American Walnut stain (Colron Wood Dye) here.
  6. Lacquer - On my first attempt with the 145, I used paint on lacquer, and reckoned that a spary lacquer would have been better. However, in the meantime I had used a spray lacquer on something else, with very dissappointing results - you need a good setup to make that work well (aerosol cans don't cut it), so this time I used a paint lacquer again.
  7. Polish - As before, I used several coats of Colron finishing wax polish. Final result front and back.
Problems this time around:
  • The louvres have come out rather badly - I should have put a great deal more effort into getting the filler smooth and even when it was wet - once hardened it was impossible to successfully sand down to a smooth and rounded finish.
  • Although the paint on lacquer was OK in principle (I still believe a proper spray would be better), I was a bit sloppy putting it on, and have left some streak marks, which is rather irritating!
M3 manual felts
Replacement up and down stop felts can be bought from Trek II (I used the standard felts and cut them down to size).

This was a straightforward job, easier than on the A100 / C3.

I removed the two short bolts at each end of the upper keyboard and slid out the music rack (what an excellent design!) I then removed the two large bolts holding the manuals in place, found underneath the front of the organ, the three metal bolts holding the manauls to the front rail, and the two wood screws holding on the lower manual cheek blocks. Finally I removed the piece of black metal along the back of the upper manual keys.

The upper manuals then raised easily, and I could undo the black bolts along the front and remove the front strip. The lower manuals could only be raised by slightly pulling away the front rail to release a small "catch" in there. But once done, removing the front strip was easy; stripped.

I peeled off the old felts, both of which were very hard, and then carefully stuck on the new felts, doing a few cm at a time and keeping them tight to the edges, and then reassembled the whole organ.

As per the A100 & C3 before it, this was the single most useful job I know of - the feel of the keys has improved beyond measure.

M3 A0-29 electrolytic capacitors
I bought a replacement preamp capacitor kit (from Tonewheel General) for my 1965 M3. This consists of two can capacitors, three ordinary electrolytics and some instructions. This was a very fiddley job; more so than on the A100 & C3 I've also done. But it did all work finally. I didn't desolder the amp - you can turn it upside down with the wires attahced.

I would say that this job is only suitable for someone with fair confidence with a soldering iron. A 'solder sucker' (to remove the old solder on the caps) was also useful.

Hammond C3 cabinet refinish
I bought a 1965 C3 in fair physical condition, but badly sun faded (it looks better in the photo than I real life), with the aim of refinishing the cabinet - I'd really like to have an immaculate Hammond, but my A100 cabinet is too damaged for me to fix (lost some veneer). This way I can also get the colour I want.
  1. Empty the cabinet - I dismantled the pedals, took out the manuals, and dismantled the lid & bench, including removing all the hinges etc; photos partly emptied, more emptied (note the set of passport photos from the early 1970s I found inside), the manuals removed, some random parts. I removed the wires from the tonegen by just cutting them off close to the solder tags, then once the tonegen was out of the organ I pulled off the bits of wire left on there (and desoldered the terminals). In the process, a few of the solder tags broke off, it was almost as though the heat of the soldering iron fatigued the metal some how? Not a serious problem though.
  2. Strip off the lacquer - This proved to be much more difficult than with the Leslies I'd previous stripped. Each panel needed at least two coats; firstly scraping with a metal 'filler' tool, and then rather more energeitcally with a proper steel 'scraper'. The blades of which went blunt in no time at all - I went through a lot of blades. I started with 'Nitromors Varish & Lacquer Remover', but was using so much I went to 'www.wood-finishes-direct.com' and bought a 5L can of stripper, which was much the same stuff, but rather more cost effective. Here's a shot of the empty cabinet being stripped - it got a lot worse before it got better ...
  3. Sand down the cabinet - This time I did give in and abandon the hand sanding. I bought a small orbital sander (Bosch PSM 80) and used 120 grain paper. This all worked rather well, though I got through a lot of sanding pads. Here's part of the lid in progress and some bits done, the bench and the cabinet.
  4. Stain - First I wiped the sanded cabinet down with a cloth damped in white spirit, then once that had dried I used 3-4 coats of Colron Wood Dye (American Walnut) - this came out to a nice deep brown; cabinet and bits. I was surprised to find that the sun fading marks were still visible on the inside of the side panels (where the manuals are), and in bits on the sides themselves - nothing showed up after sanding!
  5. Lacquer - After experimenting with painting lacquer on the underside of the bench, I decided that I really didn't have the knowledge to get a decent finish, so paid someone to do it. I had various quotes, most of them for more money that the organ was worth, but one was rather low (too low?) so I went with that. It came out pretty well!
  6. Metalwork - I cleaned up the metal work; the main hinge (which is lacquered, so first you need to put a coat of stripper on it) took a lot of work with brasso, as did all the main hinge screws - I relaquerd the hinge afterwards. To get an even finish on it, I laid the hinge flat on a thick sheet, and poured the laquer over it, rather than try and paint it on. The swell pedal coupling rod came out as shiny copper after cleaning! I never realised they were that colour! I cleaned (with cleaning wipes from a supermarket) the preamp, but didn't polish it to a shiny finish.
  7. Overhaul - I did some minor mainteance work; refelted the upper & lower manuals (essential I would say), cleaned the buss bars, replaced the preamp electrolytic caps with a set from tonewheel general. I also replaced the start/run switches with a new pair in shiny chrome (see 10A toggle switchs) , and the start/run plate with one from TrekII (the original start switch had been replaced very badly at some point in the past) - the Trek II plate looks very nice.
  8. Final - And here it is; lid open, lid closed, other side. All looking pretty good!
Add reverb to a 251
Now I have a C3, I really miss the reverb on my A100 through the 251. I could have bought a reverb unit for the C3 (Trek II or OrganMate), but then the reverb is "spun", which I tried before on my BC and didn't like. My 251 now had an "empty" channel, and so if I could add a reverb unit into it, I could send the output to that channel, aka the A100 setup.

Someone kindly gave me an A0-44 and reverb tank out of an A100. This is designed to be driven from the A100 speaker lines directly, and should be trivial to install into the 251. I mounted the amp insode the leslie on the side, driven from the 251 amp speaker out (before the crossover), and hung the reverb tray on the other side, hanging free on rubber mounts (actually some plumbing "O" rings from B&Q) - I did try screwing the tray directly to the cabinet, but then it picked up the vibrations from the bass speaker and when on the tremelo setting. I sent the reverb output back into the 251 amp - technically I could have driven the speakers directly from the A0-44, but I though I might as well use the 251 channel, then I also get a built in "volume" control.

Initially, the 251 speaker signal was far too high, distorting the reverb tray in an unpleasant way, so I put a 220ohm resistor in the A0-44 signal input (not shown in the photo), and that sorted it out, though maybe a 330ohm would have been better.

This was a pretty simple mod (if you can get hold of the amp & reverb tray!) and works fine. The reverb isn't as good as the Trek II one I once owned, but it's certainly as good as when I had my original A100 reverb driving this 251.

NOTE: Since then, I've actually connected the A0-44 output directly to the speakers via a 1k pot (in series) instead of going back through the 251 2nd channel - this does work better then trying to attenuate the signal and pushing it back up again.

Modify TrekII Reverb for 251
I bought a reverb unit from Trek II for my C3, and mounted the control pot on the console after milling a suitable hole (where the A100 reverb control would have been) and buying a blank plate to put there.

The Trek reverb sound is truly lovely, but of course is sent through the spinning Leslie - on slow or stop this is fine, but on fast I feel it sounds awfully muddy to my ears, and I wondered about sending it to my 251 stationary channel instead.

Looking at the schematic that Trek provide, it looked like a simple thing to do, and Mike at Trek II confirmed the changes I would need to make.

  • We need to only output a "wet" signal from the reverb unit. This meant breaking the input to pin 3 of IC2A and grounding it - I cut the PCB track between pin 3 and R2 with a knife, and soldered in a small wire to a suitable ground point.
  • Mike suggested replacing C2 with a 10uF capacitor & 100ohm resistor in series to reduce AC hum from the leslie. I just removed C2 and wired in a resistor & cap in its place.
  • We need to keep the signal path running through the preamp, since we're not going to mix the reverb in and return it from the unit. For this I cut the track from the old C2 to the adaptor pin 1, and then put a jumper wire from the adaptor pin 1 to pin 4 (so retaining the preamp signal),
  • Finally I wired the output from before the cut track (old C2 point) to the 251 second channel input.
I made the changes neatly and carefully so they could be reversed if ever required.

All this worked as hoped for, and the Trek reverb signal is better sounding than my previous A0-44 set up. The output of the reverb unit is perhaps slightly quiet for the 251. For my home use, with the rotoary channel on '7' and the stationary channel on '10' the levels are fine, but with the rotary on '10' you might want to boost the reverb output, probably by changing R5.

251 amp partial rebuild
I was having problems with my Leslie 251 amp; the volume would slowly diminish while playing, becoming more (quite nicely actually) distorted, and then jump back to full volume whenever I changed speeds. Rather than try and fix the problem, I decided a rebuild was a more straightforward fix for the 40 year old components. The volume controls were also almost unusably scratchy. Actually, all I went for in the end was:
  • Change all the capacitors - bought online somewhere, not orange drops, but equivalent
  • Change both pots - RS sold a suitable type
  • The four rectifier diodes - from Maplin
  • A few of the resistors, in particular the high power ones - from Maplin
I started at the diodes end, and worked my way to the controls end, replacing each component in turn. This made it a pretty straightforward job, compared to a complete strip and rebuild from scratch. I did take many photos of the components layout beforehand though, just in case, and made sure I had a schematic!

A shot of the amp from before and after.

So far it appears to have fixed the problems I was having. Measuring the old caps afterwards, they were all still on value except the .05uF "Black Cat" ones, which had risen to 0.08uF, as were the resistors I changed, so maybe just the resoldering cured it.

251 crossover cap replacement
While I had the back off the 251 for other work, I though I should replace the crossover caps in there. A quick search on the web came up with this page with some details (145/147/122/251 are all the same).
So I bought two "ANSAR SUPERSOUND Polypropylene Audio Capacitors" - an 8uF and a 12uF, which was I felt close enough to the original 7.8uF and 12.5uF values. Replacing the old unit in the crossover was trivial.
On measuring the old caps, the 12.5 now read 47uF, and the 7.8 now read 24uF.
M3 Trek ELB-1A FX loop
So I have an original 1950s UK model M3 with factory fitted reverb, of which I am very fond, but don't play that much. It's not the lack of foldback that puts me off, but the left hand - I play left hand bass, and the lowest 8' db on the M3 is a pure sine wave (rather than the M100 mixed wave) and so sounds very weak, and is also an octave too high.

So I thought I could add an octave pedal to it. Now I have an old Digitech Studio Quad which has a high quality pitch shift on it, which I tried on my C3, so I went and bought the Trek II ELB-1A for the M.

Installation is pretty straightforward. Worth noting that you don't have to get the manuals out to get into the output transformer (live and learn), and on my M3 the white wire in the amp tapped for power matches the white wire on the perc cut off pot (it's not actually obvious which terminal to use looking in the amp).

But like all Trek products, the quality was excellent and it worked just as it should. The output is too high for the M3 - trim the pot a bit to lower it. The octave works as expected, it's polyphonic, but obviously not quite the same as a TG with the lower tones on it!

Here are some schematics, scanned from the manual (many others can be found online; try Captain Foldbacks site): Need a replacement Hammond or Leslie decal? Take this PDF version to a print shop (you'll need to scale it to size first) (provided by Dave Bishop, original source unknown).

Here's a shot promo film of the Hammond Organ factory (from Peter Jones)

A story accredited to Bob Mitchell about Don Leslie creating his speaker, probably I took it from the HamTech mail list.

Complete list of all vintage Hammond & Leslie Models, including general specifications and pictures of some models.

This list was put together back in the early 1990s, when online Hammond resources were slim on the ground, and used to be "Appendix A" of the now rather defunct Hammond FAQ.

Last update 30 Jul 2013 (c) Bevis Peters (bevis@jackhollow.com)

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