T-200 Replacement Transistors

[Gjesse]

I've got a T-233 with percussion board (124-000181). It appears I have some failed transistors, Q508,Q517, and possibly Q518...see schematic
http://www.captain-foldback.com/Hamm...s/page5-10.gif
both have hammond PN 001-021172

It appears based on reading in other threads that Q508 and Q517 are replaceable with 2N3906 PNP transistors.
Is this correct?

Also, Q518 appears to be a p-channel FET. Any ideas what I should replace this with?

Onesy-twosies like this seem to be cheapest and fastest on EBAY. Is there a better source someone can suggest?

[Jyvoipabo]

I've got a T-233 with percussion board (124-000181). It appears I have some failed transistors, Q508,Q517, and possibly Q518...see schematic
http://www.captain-foldback.com/Hamm...s/page5-10.gif
both have hammond PN 001-021172

It appears based on reading in other threads that Q508 and Q517 are replaceable with 2N3906 PNP transistors.
Is this correct?

Also, Q518 appears to be a p-channel FET. Any ideas what I should replace this with?

Onesy-twosies like this seem to be cheapest and fastest on EBAY. Is there a better source someone can suggest?

Hello,

2N3906 = Universal PNP silicon transistor = OK in this application.
Remark you can buy ton's for a buck. Complementary is 2N3904.

The FETS are Voltage controled resistors.
The end of this note give popular Fet's used in this application(J111, 2N5486...)
https://www.google.fr/url?sa=t&rct=j...rPs7bjxYJlUdJM

JP

[Gjesse]

great info...thx!
Just not sure which of these makes the most sense to use as a replacement of the Q518.

[Jyvoipabo]

great info...thx!
Just not sure which of these makes the most sense to use as a replacement of the Q518.

The link you give is dead !
Here a pic with interresting notice.

We often meet these jfet in guitar amps.
They are used to switch channels.
And there are often source of failures.

Since there are 2 you can try to swap them.

JP

[Gjesse]

sorry for the bad link...it's the same as the one you posted.
thx for the info.
I went ahead and ordered j111's and 2N5486's
I guess if one doesn't work I'll try the other .
I'll report back once I've tried 'em

[Brendon Wright]

Ah! Fantastic! JP has replied.
I hadn't refreshed my page so didn't see you'd gotten help.

It takes forever to find substitutions on google for these hammond part numbers, but they DO come up if you persist.
Years back I had asked George Benton (GeoElectro) these same questions here on the forum but the posts are so hard to find!


it looks like the PN 001-021172 does indeed substitute with a a 2n3906:

https://vetco.net/products/2n3906-pnp-transistor-nte159

The word "equivalent" is worth trying if "substitute" doesn't come up with results.

There used to be a pdf with all of the Hammond/leslie solid state part equivalents.

I can't find it but there's something similar here:
http://theatreorgans.com/hammond/faq..._bulletins.htm

Go down to E-100: "Transistor and Diode Commercial Part Replacement Chart" which will help some.

Also worth looking into the part subs on the same page for the H100 and the tone cabinets.
The funny thing with these old service bulletins is that some of the listed substitutes aren't available anymore, but it's easier to find subs listed for THEM online.

- - - Updated - - -

AH!
Captain foldback has the pdf I was looking for:

http://captain-foldback.com/Hammond_...schematics.htm

look for: "Hammond Solid State Component Cross-Reference (zipped gif)"

[Gjesse]

Awesome info...thx as always Brendan!
I think I'll be needing that to replace whatever components are actually my problem...The transistor replacements on the perc board did nothing.
So i decided to step back and start with the DC volt notes on the perc board schematic (124-000181) that indicate what supply voltages the board should be getting,
and what signals should be present and where for certain tabs and keys being pressed.
It fails to meet spec in a few places, which I'm assuming is the root of the issues with my percussion.

At pin 2 and 3 it says i should have 14.5V when any key is pressed. I get 5v. With no key pressed I get 15.4, schematic says 16

At pin 6 I should have 16V keyed. I get 4mV keyed and unkeyed.

Pin 10 should be 16v keyed with any perc tab down. i get 1.4V keyed and unkeyed.

Pin 7 should have 14V keyed, I get 0.8V keyed and unkeyed

Some are in spec.
Pin 25 says 22V and I do get 22V
Pin 16 and 17 get 16V as advertised

I don't have a scope to get the P-P measurements for the AC signals, so no data on that.

Qualitatively, perc sounds come through at very low volume and the sounds change with the tabs selected, no decay, and no reiteration.

I'm thinking I need to track down the problems with my DC voltages at the pins before I dig anymore into the board components.
Just not quite sure where to start. I'm gonna hit up your buddy Chris soon and see if he has any advice as well.

[Jyvoipabo]

At pin 2 and 3 it says i should have 14.5V when any key is pressed. I get 5v. With no key pressed I get 15.4, schematic says 16
At pin 6 I should have 16V keyed. I get 4mV keyed and unkeyed.

The problem is not far.
Q508 works as a logical inverter : When input is low (pin2 = 14V5 when any key is pressed) output should be high (Pin6 = 16V). And Pin6 = 0 Volt if no key pressed.
But the 5Volts you have pin 2 when a key is pressed is unexpected.
Except if R515(22k) is open (or bad soldier near it).

JP

[Brendon Wright]

Thanks JP!
Your input is very, very much appreciated.
It's a bit beyond my depth!

[Gjesse]

Thanks JP! the solder joint at the collector on Q508 was indeed bad and now fixed.
Now I get 16v on the collector when a key is pressed, and most of my dc voltages are nominal.
Pin 2 and 3 : 15.5v unkeyed,.. 14.1 keyed
Pin 6; 0v unkeyed...16V keyed
Pin10: 16V keyed with a perc tab down
Pin 4 and 5: 21V
Pin 25: 22V
Pin 17 and 17: 16V

Here's the one problem...according to teh schematic,
Pin7 should have 14V keyed. I get:
with no tabs down: .6v unkeyed...around 5v keyed, increasing and leveling out at 10V if I hold the key down 15 seconds or so
with chimes down: .34 unkeyed....around 5v keyed, increasing to 10V if I hold the key down 15 seconds or so
with only reiteration down: 1.4v keyed or unkeyed
with chimes and reiteration down: hard to read, voltage constantly moving due to reiteration

So the sound has changed a bit. The percussion sounds are the same low volume, and don't decay just like before, but now there is a thuddy pulse noise that's superimposed on top, so it seems I'm in the right direction. The reiteration tab now works, sort of, with a thuddy pulse that repeats and the rate changes with the rate knob, same for all perc tabs including double mallets...
Ideas what to check next?
Thx everyone for all your help!

Also, A general question...the schematic says I should measure 14v keyed at pin 7...and next to pin 7 it says ‘voltage from Reiteration tab’. Does this mean that the Reiteration tab is supposed to be supplying 14v to the perc board at pin 7 with a key pressed? So if I remove the perc board from the equation and pull the wire from pin 7 I should see 14v at the wire’s clip and 0v on pin 7 right? If so then that points to an issue in the perc board I assume?
If I don’t see 14v on the wire, would that indicate a problem somewhere else besides the perc board?
Just trying to wrap my head around this schematic.

[Jyvoipabo]

Hello,

If you have a digital meter, you cannot do measurements on pulses or saw tooth signals (for example Pin7). Only a needle device or an oscilloscope is appropriate. But do not worry, for now an oscilloscope would be of little use.
If the percussion works and réiterate the sawtooth on Pin7 is OK.

I don't know the T200. Never seen the shadow of one. I simply give you some tracks.

A poor weld on the Q508 collector may not be the only one cause of the problem that existed on the Base.
Refer the data sheets (Pinout of the transistors) and make sure base, collector and emitter are in the right place.
Also, if necessary verify all the transistors you have moved.

Make a complete tour of the settings that work properly and those who do not. This includes the keys and potentiomers of the card (identify their position before).
Try to determine which ones have an action on the noise you hear.
If necessary remove connections or short drain-source pins of the Jfets.

JP

[Gjesse]

Thanks a lot for the great advice! Funny, while verifying the FET lead positions I found that there’s a discrepancy between the schematic and the silkscreen letters on the board at the q518 transistor. The pad at the Drain position marked D connects to ground and the Source pad marked S connects to C515, just the opposite of the schematic. Not sure which to believe. Neither position solves my problem - low volume percussion sounds with no decay- so it may not really matter much ...not even sure it matters at all as long as the gate is correct. Current can flow both ways through d and s right? Or is the gate voltage referenced to only the source pin which needs to be at ground or something?

[Jyvoipabo]

Hello,

Yes, it is important to respect the order of the pins always with the source to the ground.

Oops ! it is also important to respect the polarity :
N Channel. The gate is controlled by a negative pulse.
P Channel. The gate is controlled by a positive pulse. This is your case since the drawing indicates a gate with an arrow to the outside.

Accepted my confuses, PJfets is much less frequent and I gave you a bad indication.

I will try to find P Channel JFet that you can buy. This may not be very simple because many of these components are obsoletes.

Check also the old ones, they may not be dead.

JP

[Jyvoipabo]

The Fet Channel P are few, and the only one I found for this application (VCR) is :
Siliconix VCR3P still in production.
All others are switches not intended to work this way. You can nevertheless obtain results with cheaper J175 or J176

But before, you have to locate pot R356 and verify it works and give a bias from 0 to 7 Volts approx to pin 13 (bias adjust of the board).

JP

[Gjesse]

I get 0-0.7v at pin 13 when I adjust the R356 to both extremes. It actually maxes out at .7 about 1/4 of the way from minimum to maximum rotation on the pot. You mentioned I should get 0-7v. What could be the cause of me getting such a low bias range?