Hammond B250 repair and cap replacement

Recently, after having visited the Tasten-Festival at Herdecke, I felt inspired to sit down on my Hammond B250 and move my fingers. This sadly happens seldom enough, and so the organ hadn’t then been powered on for months. And although the B250 is a quite reliable oldie in my experience (just one repair within the past 10 years, a voltage regulator on the PSU had to be replaced), it now came up with a dead „G“ pedal tone.

So I first checked the pedal unit and then opened up the B250 and found a broken connector on the bass tone generator board. The pin just broke in pieces after being unclipped and pulled out of the housing (see red circles on image). With an appropriate replacement part this was quickly fixed. But there was another thing that soon concerned me much more: Electrolytic capacitors with green corroded pins.

Approximately 80 percent of all caps on the B250’s PCBs showed more or less visible signs of aging and deterioration. I started to replace a few caps on the bass tone generator board, measured their ESR and capacity values and – to my surprise – couldn’t detect any problems. »Dude«, you may say now, »it is too obvious that these caps have to be replaced«. You are right, but the organ still plays and a complete swap would mean a total of 98 caps. »Replace them immediately. They will soon lose capacity and the leaking acid will irreparably damage the PCBs «, an expert told me after I sent him a photo. Ok, I’m persuaded, this is a case of „bad caps alert“.

While removing and „recaping“ the panel PBCs I took the opportunity to refurbish the drawbars. Although my B250 lives in a smoke-free environment and a deep cleaning was not necessary, it was still a good idea to remove the dry old grease and lubricate it with fresh „white“ lithium based grease. See this excellent Hammond Service page for instructions and tips.

All in all it took two workdays to complete this operation. Below is a photo of my B250 after wakening up, and I think the organ looks happy now. The overall sound is a bit more bright and substantial, due to the all new coupling capacitors. It also smells like a new one ;-) .

Update (Jul 20, 2022):
Because of request here is the service manual of the Hammond B250. I have taken pains. :-) Drop me a line if something should be illegible.

Download service manual Hammond B250 service manual (~30 MB)

15 Responses to “Hammond B250 repair and cap replacement”

  1. Hajo’s » Blog Archive » Hammond B250 sagt:

    […] See also Hammond B250 repair and cap replacement. […]

  2. Jason sagt:

    Hi have been reading with intrest your experience with th B-250. I have just won a B-250 on Ebay Hope you don’t mind me asking but have you had any issues regarding replacement parts (it’s a rare beast only 400 made I think?) Having read the reviews I am really excited about playing this thing live whats your thoughts on the organ

    Many Thanks


    • Hajo sagt:

      Hi Jason,

      congratulations on your purchase. I like the B250 very much and still would prefer it over most of the non-Hammond clones around. As with most other organs, the B250 sounds best when run over a Leslie speaker. Besides from the few Nihon Hammond Custom-LSIs, replacement parts should not be a matter of concern.


      • Jason sagt:

        Many Thanks for the reply Hajo. I just cant stop playing this organ it really comes alive with a leslie (even the rotary sim on a Alesis Micro Verb makes a difference). In terms of playing live I will probably go with a Neo Ventilator Leslie simulator lots of good reviews for this product.



        • Hajo sagt:

          Hi Jason,

          glad to hear that you are happy with the B250. Besides the Leslie 710, I am also a proud owner of the Neo Ventilator (ordered one of the first units in 2009), and it is truly amazing! Fits perfectly with the B250.

          All the best,

  3. Graham Watkins sagt:

    I do service on Hammond, and currently am looking at a B-250 in need of some repairs. The 5-pin DIN plug at the end of the expression pedal cord has been torn off and lost. 5-pin DIN plugs are easy to get, but I cannot find any information on which color wire in the cable goes to which pin. Can you help?


  4. Paul Jonker sagt:

    Hi Hajo Great site!! I am the happy owner of two B250 and i’m so happy. True a 122 leslie or an Neo pfff magic! Best keep secret!!

  5. Sergio sagt:

    Dear Hajo,

    Have just collected a B250 with Leslie proline 815.
    The percussion section is not responding (buttons light up but
    No change to sound) can I pull the board and repair. If so which
    Board and anything to look out for?


    • Hajo sagt:

      Hi Sergio,

      sorry for the long delay. Things are not that simple, so I can not give you an instant recommendation. Please also read the comments here.

      All the best,

  6. Julian sagt:


    I’ve just read your page prior to starting restoring a B250.
    There were quite a few problems initially and so far I’ve resolved some, all the keys are working now but they’re not making the correct sound.

    For example on the upper manual with all the drawbars pushed in there is still sound produced and some of the drawbars don’t seem to have any effect over the sound.

    Lower manual some keys only make a odd screeching sound and gain some of the drawbars have no effect at all.

    I can’t see any wires broken but I do see corrosion on the caps.
    Would failed caps cause this type of problem do you think?

    Hope to hear from you soon.

    • Hajo sagt:

      Hi Julian,

      sorry, a bit late. I must admit that I have no clue wether or not the bad caps could cause the behaviour you describe. As for my B250, most of the caps were bad but the organ still sounded and behaved like an organ. But there is nothing that you might lose by replacing all caps aside from the time and labour (and the bit of money). I suppose you also already checked the supply voltages. Did you swap the IC 440 of upper and lower manual for a test?

      All the best,

  7. Tor U sagt:

    Very interesting site.
    I have just bought a B250 with midi added in very good condition and it sounds excellent through a Neo Ventilator. I am quite surprised and relieved as it sounded quite cheesy on it’s own.
    It was an impulse buy in part after reading positive comments about it on your site.
    I would like to remove the drawbar assembly to clean as they are stiff but can’t work out how to do it.
    I have taken the back off but can’t see how to get any further.
    I am nervous of causing any more problems and don’t want to disassemble any more than is necessary.
    Any advice would be gratefully appreciated.


    • Hajo sagt:

      Hi Tor,

      strictly speaking there is no quick solution and you will have to get each of the drawbar units out to clean and then lubricate it. Update: (sorry, I didn’t get you right) After the back panel it is the front panel and associated PCBs that have to be removed. See these two images. If this is certainly not an option for you, try spraying a bit of silicone grease on each of the drawbars from the back. Maybe this will do it for a start. Do not apply contact cleaner or other substances (service tipps, see section „Scratchy Drawbars“).

      Hope this helps!

      All the best,