ISO Hammond T 100 / 200 Service Manual and advice re T-211

[caseyj]

Hi,

I've been working my way through learning about the inner working of my Hammond T-211. I have found the neighbouring service manuals and some of the pages from the Hammond T 100/200 Service Manual, but not the whole thing. I'm looking for all the step by step instructions and drawings including voltage measurement points and calibration, etc.

Any other resources or advice on servicing this model of organ would be appreciated. A few things I'm working on sorting out:

- how to get proper DC supply voltages levels after changing the power supply filter caps
- how to get a clear non-fuzzy signal reading from the tone generator outputs using a scope. I'm not sure if it is due to hf signal noise somewhere, the low signal level, the probe, syncing issues, grounding, etc).
- also seeing all around lower than specified signal output levels from the tone generator. Capacitance drift on the fq filter circuits? magnetization of the tone wheels themselves? improper set up of pick up distance across the board? but that seems unlikely).
- adding a grounded plug. I've done it (I believe correctly and successfully), just wanted to see how other people approach this. I checked for current leakage from chassis to earth ground through a 10k resistor and saw very low voltage across it. I added fuses to both secondaries and the hot primary, replaced the across the line filter cap with a proper safety cap, drilled out the chassis and used a quality cable and strain relief gland.
- also hearing a louder key click on some of the drawbars compared to others, but I'm thinking this could be the reflection of the low output level from the tone generator on some drawbar setting, relative to the click noise of the contacts.
- also have seen a little bit of finicky behaviour in the switching of the bass pedal notes since changing the power supply filter caps

Thanks!

Casey

[Brendon Wright]

Hiya Casey!
I've got the full manual here but haven't got around to scanning it yet.

As you make observations on the workings, note 'em down in a doc file, it's amazing how easily ya can forget that stuff...

The T500 manual has some useful notes in it too, so it's good to have that as well as the early T stuff from Captain foldback.
Here's the T500 manual...

If you've replaced the PS caps with values as close to original as you can get, the voltages produced should be close enough.
I know modern capacitor values aren't always the same. One of my caps had to be replaced with two in parallel to get close to the original value.

For the scope question, post another thread asking for that specifically. It's quite possible any knowledgeable scope jockeys didn't read past the title.

Perhaps the same about the TG question! Post a new thread, TG's are interesting to every Hammond player, while T-series may not be.
For that matter, Kon Zissis is likely to visit such a thread, he's very keen on scope readings of the TG!

Is the TG signal significantly low?
It'll be interesting to compare them to Kon's spreadsheet of readings, especially to the other T's. My own T500 is in there somewhere!

My T was built in Australia in 1975 and bought in New Zealand, where grounded plugs were standard. The "Earth" wire was just bolted to chassis, if I recall.

The bass pedal notes could be as simple as dust in the contacts or disturbed wires. What way are they sounding finicky?

The key click question could be worth asking in a separate thread too, trick the "non T players" into the discussion!
Which drawbars are clicking more than the others?

[caseyj]

Hi Brendon,

Thank you for the extremely thoughtful reply. I am new to the forum, and this is all much appreciated.

I'll reply line by line in caps to your message:


Hiya Casey!
I've got the full manual here but haven't got around to scanning it yet.

AWESOME, THANKS.


As you make observations on the workings, note 'em down in a doc file, it's amazing how easily ya can forget that stuff...

YES, THANKS, I'VE BEEN RELUCTANT TO TAKE EXTENSIVE NOTES, BUT REGRET IT EVERY TIME I CHANGE SOMETHING AND WANT TO RECAL SOME LONG LOST MEASUREMENT FOR A TROUBLESHOOTING CLUE.

The T500 manual has some useful notes in it too, so it's good to have that as well as the early T stuff from Captain foldback.
Here's the T500 manual...
THANKS, YES I'VE GOT THIS ONE AND HAVE USED IT EXTENSIVELY.


If you've replaced the PS caps with values as close to original as you can get, the voltages produced should be close enough.
I know modern capacitor values aren't always the same. One of my caps had to be replaced with two in parallel to get close to the original value.

THANKS, YES, I'VE REPLACED THEM PRETTY CLOSE TO THEIR SPECCED CAPACITANCE AND SLIGHTLY HIGHER VOLTAGE RATING, SO I GUESS AS YOU SAID THIS SHOULD NOT BE A FACTOR. IT MAY BE RELATED TO SOME RESISTORS I CHANGED, ALSO TO THE SAME SPEC VALUE, BUT MAYBE THE ONES THAT WERE IN THERE HAD DRIFTED, AND OTHER BIAS SETTING HAD BEEN ADJUSTED PREVIOUSLY TO THOSE DRIFTED VALUES? I'LL CHECK.


For the scope question, post another thread asking for that specifically. It's quite possible any knowledgeable scope jockeys didn't read past the title.

WILL DO. I REALIZE IT MAY BE DUE TO USING A 10X ATTENUATED PROBE, WHICH MIGHT BE HARD FOR FOR SCOPE TO READ AT LOW VOLTAGE LEVELS. WILL TRY WITH 1X

Perhaps the same about the TG question! Post a new thread, TG's are interesting to every Hammond player, while T-series may not be.
For that matter, Kon Zissis is likely to visit such a thread, he's very keen on scope readings of the TG!

NOTED

Is the TG signal significantly low?
It'll be interesting to compare them to Kon's spreadsheet of readings, especially to the other T's. My own T500 is in there somewhere!

THANKS FOR THE REFERENCE, IT LOOKS LIKE I WAS LOOKING AT KON'S PAGE: http://www.dairiki.org/HammondWiki/T...orOutputLevels

FROM A CURSORY ASSESSMENT, MY READINGS DID LOOK A BIT LOW, BUT I WILL NEED TO COMPARE THE SPECIFICS ACCORDING TO THE MODEL AND THE OUTPUT #




My T was built in Australia in 1975 and bought in New Zealand, where grounded plugs were standard. The "Earth" wire was just bolted to chassis, if I recall.

The bass pedal notes could be as simple as dust in the contacts or disturbed wires. What way are they sounding finicky?

I HAVE CLEANED AND TESTED THE PEDAL CONTACTS PREVIOUSLY, SO I DON'T THINK IT IS THAT. EVERY SO OFTEN A PEDAL WILL SWITCH BETWEEN OTHER PEDAL TONES, I THINK IT MIGHT HAVE SOMETHING TO DO WITH THE SWITCHING CIRCUIT.

The key click question could be worth asking in a separate thread too, trick the "non T players" into the discussion!
Which drawbars are clicking more than the others?[/QUOTE]
NOTED, I WILL CHECK .



THANKS VERY MUCH AGAIN.
CASEY

[Brendon Wright]

BUT MAYBE THE ONES THAT WERE IN THERE HAD DRIFTED, AND OTHER BIAS SETTING HAD BEEN ADJUSTED PREVIOUSLY TO THOSE DRIFTED VALUES?

It's probably unlikely that someone would replace resistors in the power supply and not the capacitors which were causing any power supply problem.

It appears from mucking around with my own T that there's a fairly high tolerance on the values required from the power supply and it's not the sort of system that follow the recommended readings perfectly.
As long as they're in the ball park.
The same goes for the TG readings, it's possible they're (as a group) not significantly off, though one or two notes might be worth recalibrating individually.

Last year I completely rebuilt my power supply, starting with a toroidal transformer and rehousing the supply in a separate metal box. It's the quietest my T's EVER been.
Unfortunately a perc problem had me cornered so the organ's been put aside. (I also had the important parts from a dead M100 tempting me to a transplant. That was too big a dilemma to face... to fix the T for the sake of my lovely new power supply or....)

The pedals have always been a thorn in my side. I've had a lot of problems with them and fixed them only by luck, I've had similar issues with them as you're describing but I never noted the cure on paper. Usually a lot of blowing in case of dust and fumbling with the wires.

Check with Hammond Zone (newly moved to https://groups.io/g/hammondzone) and see if Chris Clifton can suggest a solution.
Though it's a nuisance, it's useful to post his suggestions here, since they'll appear in web searches.
Hammond Zone and its archive is, or at least was when under Yahoo, not available on google searches. (It is or was members only access, so you'd have to join to get Chris's help)

[caseyj]

Hi Brandon,

Thanks very much, I appreciate it.

I solve some of my tone generator measurement problems and discussed related things on this new post.

https://www.organforum.com/forums/sh...t=Oscilloscope

Best,
Casey