On Dec 7, 2024, at 9:05 AM, Ned Lucas via groups.io <nedlucas@...> wrote:

?Thank you so much!

On Dec 7, 2024, at 4:31 AM, Christoph via groups.io <kuku@...> wrote:

?Oh, typos:

unfortunately. I just wanted

Am 07.12.2024 um 10:22 schrieb Christoph via <kuku@...>:

Ned,

did you check the power supply voltages ??

Funnily, the other day I was able to download?

the T-500 Service manual from?.

Unfotunately I forgot to download part II, which contains most of the circuit diagrams. I kusted wanted to lookup the points where to measure the 15 and 35V.

unfortunately. I just wanted ... ?15 and 25V

When I try to dowload it now I‘m getting

?Item not available due to issues with theitem‘s content“ Anyone knowing an alternate source?

—

Christoph?

On Dec 7, 2024, at 4:31 AM, Christoph via groups.io <kuku@...> wrote:

?Oh, typos:

unfortunately. I just wanted

Am 07.12.2024 um 10:22 schrieb Christoph via <kuku@...>:

Ned,

did you check the power supply voltages ??

Funnily, the other day I was able to download?

the T-500 Service manual from?.

Unfotunately I forgot to download part II, which contains most of the circuit diagrams. I kusted wanted to lookup the points where to measure the 15 and 35V.

unfortunately. I just wanted ... ?15 and 25V

When I try to dowload it now I‘m getting

?Item not available due to issues with theitem‘s content“ Anyone knowing an alternate source?

—

Christoph?

Am 07.12.2024 um 10:31 schrieb Christoph Kukulies <kuku@...>:

Oh, typos:

unfortunately. I just wanted

Am 07.12.2024 um 10:22 schrieb Christoph via <kuku@...>:

Ned,

did you check the power supply voltages ??

Funnily, the other day I was able to download?

the T-500 Service manual from?.

Unfotunately I forgot to download part II, which contains most of the circuit diagrams. I kusted wanted to lookup the points where to measure the 15 and 35V.

unfortunately. I just wanted ... ?15 and 25V

When I try to dowload it now I‘m getting

?Item not available due to issues with theitem‘s content“ Anyone knowing an alternate source?

—

Christoph?

Am 07.12.2024 um 09:08 schrieb Chris Clifton via groups.io <clifton.christopher@...>:

?

There should be a picture of the board with the components labelled in your service manual.

On 06/12/2024 22:26, Ned Lucas via groups.io wrote:

Thanks. I’ll check the transistor voltages but how do I know what transistor on the schematic is which transistor on the board?

On Dec 6, 2024, at 2:08 PM, Chris Clifton via groups.io <clifton.christopher@...> wrote:

?

The transistors you've labelled 1 & 2 are part of the reverb drive amplifier. They provide the signal fed into the input end of the reverb springs. As such, they have no direct connection with the main organ signal, but a fault here could affect power supplies common to the reverb drive and main amplifiers. They might get warm when the organ is operating, but should not get hot enough to be uncomfortable, or even painful to touch. The transistor in the black heat sink (#3) is the driver for the output transistors of the main amp. Them"2111 etc. part number is the Hammond part number for these transistors, the one in the heat sink is a similar transistor. Resistance checks around the transistors really won't tell us much. Measuring the voltages at the emitter, base and collector pins with the organ powered up, and comparing these voltages with the voltages given on the schematic will be much more helpful. Take great care when measuring not to short the transistor leads to each other or anything else with your meter probes. The highest voltage on the amplifier board is about 25 volts. This won't hurt you, but could easily destroy transistors or other components if you accidentally create a short circuit.

On 06/12/2024 00:40, Ned Lucas via groups.io wrote:

Hi Chris,

I’ve checked all the transistors on the pwr & reverb amp board (with the organ off) using an analog multimeter on the 1x ohm setting. All check out “ok” except the 2 metal can ones and the large black one. On those I got ?some leakage when connecting to the emitter and common. I noticed that with the organ running, can #1 got very hot to the touch. The metal cans (1&2) look like they have “2111-1 6847” on them. No idea what the black (#3) is. Also, when testing #3 across E - C, the speaker made a little crackling sound.?

Am I heading in the right direction?

On Dec 4, 2024, at 10:27 AM, Chris Clifton via groups.io <clifton.christopher@...> wrote:

?

If I recall, you said that the loud background hum wasn't affected by the swell pedal. The signal at pin 8 goes through the swell before going to the actual input of the amplifier. As the hum level is unaffected by the swell pedal, this suggests that the source of the hum, (possibly also the cause of the loss of wanted signal) is somewhere on the amplifier board. The signal after the swell pedal goes in turn through Q6021, Q602, Q603 and 604 to the driver transformer, and then to the output transistors Q605 and 606. Checking the voltages around the first four transistors may give us a clue.

On 04/12/2024 14:54, Ned Lucas via groups.io wrote:

Thanks. When I tested these points the schematic said to have key #25 down with upper drawbar 8’ out and expression pedal down. Also, I wondered if my multimeter was unable to read mv since I was looking for p-p. My lowest scale on the meter is 0-25 vac. Don’t have an oscilloscope. I was able to hear a very slight sound of notes ?(under the electrical hum) if I held a full chord down with all the drawbars out. I guess I try reading component values going through the power amp board since I think the TWG is delivering a signal to it.?

On Dec 3, 2024, at 3:19 PM, Chris Clifton via groups.io <clifton.christopher@...> wrote:

?

I shouldn't worry too much about voltages at the percussion board to start with, a fault here would only affect the percussion voices.

Pin 8 on the power amp board is signal input to the amplifier. Somewhere in the service manual there will be a set of conditions, (Something like U/M drawbar tab down, certain drawbars pulled out and particular key or keys played). If all is well playing the organ as specified for the test should give a signal at this point which can be observed on an oscilloscope. Note that the voltage is specified as peak to peak, which can only be measured on a 'scope, a meter reading RMS AC volts will read something less than half the P~P voltage. Pin 6 is return from the reverb tabs, there will only be signal here with reverb tabs down, and notes being played on the organ. Pin 19 is output to the speaker system, again, there will only be an AC signal voltage here if the organ is being played. There should never be a significant DC voltage here. Pin 2 on the power amp is DC power to part of the amplifier. Nominally +15 volts, I wouldn't worry if it isn't exactly +15.

I'm struggling a bit here, I no longer have the library of paper manuals that I used when I was working. I only have some downloaded scans which seem to be missing a lot of the useful text.

On 02/12/2024 22:34, Ned Lucas via groups.io wrote:

Hi Chris - I've started to check different voltages of 2 of the boards.? I started looking at the Percussion board.?

?

At pin 10 with the perc. tab down I get 16 vdc? ? should be 16 vdc? ? ? ? ? ? INPUT VOLTAGE FROM PRESET TABS

At pin 7? ? ? "? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? I get 2.5 vdc? (it should be 14 vdc)? ? ? ? ?INPUT FROM REITERATION TAB

At pin 2? ? ?"? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?I get 14.5 vdc? should be 14.5 vdc? ? ? ? ?TO PERCUSSION KEYING

?

On the power amp board:

?

#8 = 0 mv should be 800 mv? ? (FROM PIN #3 RECOVERY & NON-VIBRATO 800MV P-P)

#2 = 16 v? should be 15v? ? ? ? ??

#6 = 0 mv should be 500 mv

#19 = 0 v? should be 15v

?

So somethings not right ...

--

--

--

--

On Dec 6, 2024, at 2:08 PM, Chris Clifton via groups.io <clifton.christopher@...> wrote:

?

The transistors you've labelled 1 & 2 are part of the reverb drive amplifier. They provide the signal fed into the input end of the reverb springs. As such, they have no direct connection with the main organ signal, but a fault here could affect power supplies common to the reverb drive and main amplifiers. They might get warm when the organ is operating, but should not get hot enough to be uncomfortable, or even painful to touch. The transistor in the black heat sink (#3) is the driver for the output transistors of the main amp. Them"2111 etc. part number is the Hammond part number for these transistors, the one in the heat sink is a similar transistor. Resistance checks around the transistors really won't tell us much. Measuring the voltages at the emitter, base and collector pins with the organ powered up, and comparing these voltages with the voltages given on the schematic will be much more helpful. Take great care when measuring not to short the transistor leads to each other or anything else with your meter probes. The highest voltage on the amplifier board is about 25 volts. This won't hurt you, but could easily destroy transistors or other components if you accidentally create a short circuit.

On 06/12/2024 00:40, Ned Lucas via groups.io wrote:

Hi Chris,

I’ve checked all the transistors on the pwr & reverb amp board (with the organ off) using an analog multimeter on the 1x ohm setting. All check out “ok” except the 2 metal can ones and the large black one. On those I got ?some leakage when connecting to the emitter and common. I noticed that with the organ running, can #1 got very hot to the touch. The metal cans (1&2) look like they have “2111-1 6847” on them. No idea what the black (#3) is. Also, when testing #3 across E - C, the speaker made a little crackling sound.?

Am I heading in the right direction?

On Dec 4, 2024, at 10:27 AM, Chris Clifton via groups.io <clifton.christopher@...> wrote:

?

If I recall, you said that the loud background hum wasn't affected by the swell pedal. The signal at pin 8 goes through the swell before going to the actual input of the amplifier. As the hum level is unaffected by the swell pedal, this suggests that the source of the hum, (possibly also the cause of the loss of wanted signal) is somewhere on the amplifier board. The signal after the swell pedal goes in turn through Q6021, Q602, Q603 and 604 to the driver transformer, and then to the output transistors Q605 and 606. Checking the voltages around the first four transistors may give us a clue.

On 04/12/2024 14:54, Ned Lucas via groups.io wrote:

Thanks. When I tested these points the schematic said to have key #25 down with upper drawbar 8’ out and expression pedal down. Also, I wondered if my multimeter was unable to read mv since I was looking for p-p. My lowest scale on the meter is 0-25 vac. Don’t have an oscilloscope. I was able to hear a very slight sound of notes ?(under the electrical hum) if I held a full chord down with all the drawbars out. I guess I try reading component values going through the power amp board since I think the TWG is delivering a signal to it.?

On Dec 3, 2024, at 3:19 PM, Chris Clifton via groups.io <clifton.christopher@...> wrote:

?

I shouldn't worry too much about voltages at the percussion board to start with, a fault here would only affect the percussion voices.

Pin 8 on the power amp board is signal input to the amplifier. Somewhere in the service manual there will be a set of conditions, (Something like U/M drawbar tab down, certain drawbars pulled out and particular key or keys played). If all is well playing the organ as specified for the test should give a signal at this point which can be observed on an oscilloscope. Note that the voltage is specified as peak to peak, which can only be measured on a 'scope, a meter reading RMS AC volts will read something less than half the P~P voltage. Pin 6 is return from the reverb tabs, there will only be signal here with reverb tabs down, and notes being played on the organ. Pin 19 is output to the speaker system, again, there will only be an AC signal voltage here if the organ is being played. There should never be a significant DC voltage here. Pin 2 on the power amp is DC power to part of the amplifier. Nominally +15 volts, I wouldn't worry if it isn't exactly +15.

I'm struggling a bit here, I no longer have the library of paper manuals that I used when I was working. I only have some downloaded scans which seem to be missing a lot of the useful text.

On 02/12/2024 22:34, Ned Lucas via groups.io wrote:

Hi Chris - I've started to check different voltages of 2 of the boards.? I started looking at the Percussion board.?

?

At pin 10 with the perc. tab down I get 16 vdc? ? should be 16 vdc? ? ? ? ? ? INPUT VOLTAGE FROM PRESET TABS

At pin 7? ? ? "? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? I get 2.5 vdc? (it should be 14 vdc)? ? ? ? ?INPUT FROM REITERATION TAB

At pin 2? ? ?"? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?I get 14.5 vdc? should be 14.5 vdc? ? ? ? ?TO PERCUSSION KEYING

?

On the power amp board:

?

#8 = 0 mv should be 800 mv? ? (FROM PIN #3 RECOVERY & NON-VIBRATO 800MV P-P)

#2 = 16 v? should be 15v? ? ? ? ??

#6 = 0 mv should be 500 mv

#19 = 0 v? should be 15v

?

So somethings not right ...

--

--

--

On Dec 4, 2024, at 10:27 AM, Chris Clifton via groups.io <clifton.christopher@...> wrote:

?

If I recall, you said that the loud background hum wasn't affected by the swell pedal. The signal at pin 8 goes through the swell before going to the actual input of the amplifier. As the hum level is unaffected by the swell pedal, this suggests that the source of the hum, (possibly also the cause of the loss of wanted signal) is somewhere on the amplifier board. The signal after the swell pedal goes in turn through Q6021, Q602, Q603 and 604 to the driver transformer, and then to the output transistors Q605 and 606. Checking the voltages around the first four transistors may give us a clue.

On 04/12/2024 14:54, Ned Lucas via groups.io wrote:

Thanks. When I tested these points the schematic said to have key #25 down with upper drawbar 8’ out and expression pedal down. Also, I wondered if my multimeter was unable to read mv since I was looking for p-p. My lowest scale on the meter is 0-25 vac. Don’t have an oscilloscope. I was able to hear a very slight sound of notes ?(under the electrical hum) if I held a full chord down with all the drawbars out. I guess I try reading component values going through the power amp board since I think the TWG is delivering a signal to it.?

On Dec 3, 2024, at 3:19 PM, Chris Clifton via groups.io <clifton.christopher@...> wrote:

?

I shouldn't worry too much about voltages at the percussion board to start with, a fault here would only affect the percussion voices.

Pin 8 on the power amp board is signal input to the amplifier. Somewhere in the service manual there will be a set of conditions, (Something like U/M drawbar tab down, certain drawbars pulled out and particular key or keys played). If all is well playing the organ as specified for the test should give a signal at this point which can be observed on an oscilloscope. Note that the voltage is specified as peak to peak, which can only be measured on a 'scope, a meter reading RMS AC volts will read something less than half the P~P voltage. Pin 6 is return from the reverb tabs, there will only be signal here with reverb tabs down, and notes being played on the organ. Pin 19 is output to the speaker system, again, there will only be an AC signal voltage here if the organ is being played. There should never be a significant DC voltage here. Pin 2 on the power amp is DC power to part of the amplifier. Nominally +15 volts, I wouldn't worry if it isn't exactly +15.

I'm struggling a bit here, I no longer have the library of paper manuals that I used when I was working. I only have some downloaded scans which seem to be missing a lot of the useful text.

On 02/12/2024 22:34, Ned Lucas via groups.io wrote:

Hi Chris - I've started to check different voltages of 2 of the boards.? I started looking at the Percussion board.?

?

At pin 10 with the perc. tab down I get 16 vdc? ? should be 16 vdc? ? ? ? ? ? INPUT VOLTAGE FROM PRESET TABS

At pin 7? ? ? "? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? I get 2.5 vdc? (it should be 14 vdc)? ? ? ? ?INPUT FROM REITERATION TAB

At pin 2? ? ?"? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?I get 14.5 vdc? should be 14.5 vdc? ? ? ? ?TO PERCUSSION KEYING

?

On the power amp board:

?

#8 = 0 mv should be 800 mv? ? (FROM PIN #3 RECOVERY & NON-VIBRATO 800MV P-P)

#2 = 16 v? should be 15v? ? ? ? ??

#6 = 0 mv should be 500 mv

#19 = 0 v? should be 15v

?

So somethings not right ...

--

--

On Dec 3, 2024, at 3:19 PM, Chris Clifton via groups.io <clifton.christopher@...> wrote:

?

I shouldn't worry too much about voltages at the percussion board to start with, a fault here would only affect the percussion voices.

Pin 8 on the power amp board is signal input to the amplifier. Somewhere in the service manual there will be a set of conditions, (Something like U/M drawbar tab down, certain drawbars pulled out and particular key or keys played). If all is well playing the organ as specified for the test should give a signal at this point which can be observed on an oscilloscope. Note that the voltage is specified as peak to peak, which can only be measured on a 'scope, a meter reading RMS AC volts will read something less than half the P~P voltage. Pin 6 is return from the reverb tabs, there will only be signal here with reverb tabs down, and notes being played on the organ. Pin 19 is output to the speaker system, again, there will only be an AC signal voltage here if the organ is being played. There should never be a significant DC voltage here. Pin 2 on the power amp is DC power to part of the amplifier. Nominally +15 volts, I wouldn't worry if it isn't exactly +15.

I'm struggling a bit here, I no longer have the library of paper manuals that I used when I was working. I only have some downloaded scans which seem to be missing a lot of the useful text.

On 02/12/2024 22:34, Ned Lucas via groups.io wrote:

Hi Chris - I've started to check different voltages of 2 of the boards.? I started looking at the Percussion board.?

?

At pin 10 with the perc. tab down I get 16 vdc? ? should be 16 vdc? ? ? ? ? ? INPUT VOLTAGE FROM PRESET TABS

At pin 7? ? ? "? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? I get 2.5 vdc? (it should be 14 vdc)? ? ? ? ?INPUT FROM REITERATION TAB

At pin 2? ? ?"? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?I get 14.5 vdc? should be 14.5 vdc? ? ? ? ?TO PERCUSSION KEYING

?

On the power amp board:

?

#8 = 0 mv should be 800 mv? ? (FROM PIN #3 RECOVERY & NON-VIBRATO 800MV P-P)

#2 = 16 v? should be 15v? ? ? ? ??

#6 = 0 mv should be 500 mv

#19 = 0 v? should be 15v

?

So somethings not right ...

--

On Nov 26, 2024, at 4:51 AM, Chris Clifton via groups.io <clifton.christopher@...> wrote:

?

You will need a schematic, you can download some here, . I'd start by trying to localise the fault. Does the hum volume vary with the swell pedal? If you put the reverb tabs down and touch the reverb springs is there a noise in the speaker? Checks like this will tell you what is working and help localise the fault. From memory, the push on pin connectors to the various circuit boards can develop bad connections over time. As there are many of them best to try to find the area of the problem first. There are several signal paths through the organ. For example, upper and lower manual are separate before the vibrato tabs. After vibrato tabs, there are two signal routes, vibrato and non-vibrato. If you have no sound with vibrato on or off from either manual, it's unlikely that your main problem is in this area. You may find a problem here after you've fixed the main problem though. You will just have to work methodically through the organ tracing the signal. Given the symptoms, I'd probably start at the output, speaker end, and work backwards. You can hear a hum, speakers are good. The hum could be symptomatic of an amplifier fault (probably not if it varies with swell pedal setting and, or the reverb springs will make a noise in the speakers).

On 26/11/2024 02:55, Ned Lucas via groups.io wrote:

Thanks Chris - I’ve searched on some of your threads so you don’t have to reinvent the wheel in helping me. Is there maybe a particular thread you could steer me to that will help me step through the steps you would take?

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