I suspect that the output impedance of the original tone generator pick ups will also be quite reactive, probably inductive. The transient produced when a key contact makes will likely be a short lived oscillation, producing the characteristic click we know and love. The output of an electronic TG substitute will likely be closer to a pure resistance.

---

From: [email protected] on behalf of Christoph via
Sent: Sunday, January 07, 2024 12:17
To: [email protected]
Subject: Re: [hammondzone] How to fix a broken TG pickup screw

Happy New Year, everyone.

Hi Matyas, hi Scott,

as much as I estimate your expertise, Scott, ?I would like to tell you about an experience I recently made with a B3 having such a TrekII GNR-1A GENERATOR NOTE REPLACEMENT unit established.?

TG Note D ?(#39) was missing and had been substituted by the Trek unit.

The funny thing: the sound of the note when it started to make contact to the busbar was different from the neighbor notes (wcoming ?from the tonewheels, of course). The sound was a thumping noise, not the precise clicking, one is used to. The note was sustaining, of course, but the attack was different from the ?TG-generated notes and appeared unpleasant to me, somehow thumping, muted, not so crisp. It could be caused by the fact that the signal source of the originally generated not is extremely low ohm (current switch) while the note coming from the opamp of the Trek unit has a different source impedance (higher).

making producing excellent products but in this particular case I would recommend if you are a person with so much skills like you, I'd dispense with using this substitution method and try it the hard way:?

get out the screw(s) (there are two in your case IIRC) mechanically.

In a first attempt I would try to adjust the magnets even though the screws on their collars are broken off.?

With a pair of pliers (string cutter) ?it might be possible to pull out the magnet rods to some extent and using a copper or brass hammer it would be possible to adjust the signal.

If that doesn't work or isn't desired, the other method would be, to get off the?

1. get the TG out of the organ and put it on a table.

2. loosen the flat rails that are holding the phenolic guides for the magnet rods.

3. get out all screws that are fixing the side walls against the TG

4. lift off the side walls.

5. get at the magnet rod in question and drive out the rod from the collar.

6. once done this the broken thread piece of the collar screw can be fiddled out using a watchmaker's ?screwdriver.?

? ?Eventually a diamond bit of a dremel tool can help .

All in all it's a long winded and delicate work but it pays off.

--

Christoph

Some pictures can be found here:

Am 05.01.2024 um 20:28 schrieb Mátyás Premecz <matyooo@...>:

Hi Scott!

Thank you for your reply!

We were considering the TrekII or other simple sine wave generator solution. But the fact that there were two open coils (300+ USD) and the purist approach of the owner prevented that from happening.

I could get replacement pickups, and figured for the price with shipping and customs and VAT I could easily do the job. The one thing I did not see coming is the screws breaking. However I managed to pull the pickups with the broken screws with a small chuck (not the open coils that were?replaced, but other two that I broke during recalibration), so the recalibration was done anyway.?

I am just looking for a way to tidy things up for the next Hammond tech looking at this organ in 20 years....

Greetings,

Matyas

Scott Hawthorn <organfreak@...> ezt írta (id?pont: 2024. jan. 5., P, 17:57):

Use the Trek II note-replacement kit. It is easy to install and works perfectly.

On 1/5/2024 12:33 AM, Mátyás Premecz wrote:

Dear Group!

I need your collective?mechanical wisdom on?removing broken?screws.

I am in the middle of fixing a Hammond RT3 that was in the shed for twenty years. Now, I have been fixing Hammonds for almost ten years now but I never had to replace?broken coils in the?generator. This organ had two open coils (51 and 56) which I could successfully replace with parts from a donor generator. Everything should be great but I broke two of the pickup holder screws during recalibration (I?recapped the?TG as well).?

They are in the middle row so access is very limited. No chance to access it with a normal or even a mini drill (Dremel is too big). One of them has nothing to hold on, it broke inside its?hole. (Happy side note: I could do the calibration anyway because I could move them with a small chuck.)

Even if I leave things as they are now, the organ is saved so it's a win but I would try to maintain the integrity of the organ if possible.

So, what do you do with those?

Thank you very much!

Matyas Premecz

Am 05.01.2024 um 20:28 schrieb Mátyás Premecz <matyooo@...>:

Hi Scott!

Thank you for your reply!

We were considering the TrekII or other simple sine wave generator solution. But the fact that there were two open coils (300+ USD) and the purist approach of the owner prevented that from happening.

I could get replacement pickups, and figured for the price with shipping and customs and VAT I could easily do the job. The one thing I did not see coming is the screws breaking. However I managed to pull the pickups with the broken screws with a small chuck (not the open coils that were?replaced, but other two that I broke during recalibration), so the recalibration was done anyway.?

I am just looking for a way to tidy things up for the next Hammond tech looking at this organ in 20 years....

Greetings,

Matyas

Scott Hawthorn <organfreak@...> ezt írta (id?pont: 2024. jan. 5., P, 17:57):

Use the Trek II note-replacement kit. It is easy to install and works perfectly.

On 1/5/2024 12:33 AM, Mátyás Premecz wrote:

Dear Group!

I need your collective?mechanical wisdom on?removing broken?screws.

I am in the middle of fixing a Hammond RT3 that was in the shed for twenty years. Now, I have been fixing Hammonds for almost ten years now but I never had to replace?broken coils in the?generator. This organ had two open coils (51 and 56) which I could successfully replace with parts from a donor generator. Everything should be great but I broke two of the pickup holder screws during recalibration (I?recapped the?TG as well).?

They are in the middle row so access is very limited. No chance to access it with a normal or even a mini drill (Dremel is too big). One of them has nothing to hold on, it broke inside its?hole. (Happy side note: I could do the calibration anyway because I could move them with a small chuck.)

Even if I leave things as they are now, the organ is saved so it's a win but I would try to maintain the integrity of the organ if possible.

So, what do you do with those?

Thank you very much!

Matyas Premecz

Use the Trek II note-replacement kit. It is easy to install and works perfectly.

On 1/5/2024 12:33 AM, Mátyás Premecz wrote:

Dear Group!

I need your collective?mechanical wisdom on?removing broken?screws.

I am in the middle of fixing a Hammond RT3 that was in the shed for twenty years. Now, I have been fixing Hammonds for almost ten years now but I never had to replace?broken coils in the?generator. This organ had two open coils (51 and 56) which I could successfully replace with parts from a donor generator. Everything should be great but I broke two of the pickup holder screws during recalibration (I?recapped the?TG as well).?

They are in the middle row so access is very limited. No chance to access it with a normal or even a mini drill (Dremel is too big). One of them has nothing to hold on, it broke inside its?hole. (Happy side note: I could do the calibration anyway because I could move them with a small chuck.)

Even if I leave things as they are now, the organ is saved so it's a win but I would try to maintain the integrity of the organ if possible.

So, what do you do with those?

Thank you very much!

Matyas Premecz

Dear Group!

I need your collective?mechanical wisdom on?removing broken?screws.

I am in the middle of fixing a Hammond RT3 that was in the shed for twenty years. Now, I have been fixing Hammonds for almost ten years now but I never had to replace?broken coils in the?generator. This organ had two open coils (51 and 56) which I could successfully replace with parts from a donor generator. Everything should be great but I broke two of the pickup holder screws during recalibration (I?recapped the?TG as well).?

They are in the middle row so access is very limited. No chance to access it with a normal or even a mini drill (Dremel is too big). One of them has nothing to hold on, it broke inside its?hole. (Happy side note: I could do the calibration anyway because I could move them with a small chuck.)

Even if I leave things as they are now, the organ is saved so it's a win but I would try to maintain the integrity of the organ if possible.

So, what do you do with those?

Thank you very much!

Matyas Premecz

Only T- series organs were produced with both types of scanner as far as I know. Some later models were only made with drum scanners (H-series?). Electrically, the capacitance between stator and rotor in the scanner would act as a high pass/low stop filter in conjunction with the input impedance of the vibrato recovery amp. As long as the capacitance is large enough to allow the lowest frequencies required to pass, the exact value wouldn't be critical. Most, if not all, all the organs that were equipped with drum scanners didn't put vibrato on bass pedal signals, so the very lowest notes in the organ didn't go through the vibrato scanner anyway.

On 30/07/2023 12:02, Chris Clifton via groups.io wrote:

To the best of my knowledge, their are no differences in the vibrato drive, vibrato line, or vibrato recovery circuits used in organs with either type of scanner. The schematics for early T-series organs and later organs including the T-500 show no differences. I think that it's safe to assume that either scanner type is electrically equivalent to the other. Mechanically, of course they are very different.

On 30/07/2023 10:46, Uwe Menrath wrote:

Hi,

I've seen different types of vibrato scanners in otherwise similar organs: My TTR-100 has a self starting motor, it's scanner is of the same pan type as in consoles from B-2, C-2 etc. on, but mounted at the opposite generator end (where the big consoles would have their start motor). My TTR-200 and T-200 have basically the same generator, but with a drum scanner mounted next to the self starting motor. As the delay lines in these organs appear to be the same, I think both scanner types show indentical capacitance values between the rotor and the stator plates. Am I correct?

Best regards!

--

--

Am 30.07.2023 um 13:02 schrieb Chris Clifton <clifton.christopher@...>:

To the best of my knowledge, their are no differences in the vibrato drive, vibrato line, or vibrato recovery circuits used in organs with either type of scanner. The schematics for early T-series organs and later organs including the T-500 show no differences. I think that it's safe to assume that either scanner type is electrically equivalent to the other. Mechanically, of course they are very different.

On 30/07/2023 10:46, Uwe Menrath wrote:

Hi,

I've seen different types of vibrato scanners in otherwise similar organs: My TTR-100 has a self starting motor, it's scanner is of the same pan type as in consoles from B-2, C-2 etc. on, but mounted at the opposite generator end (where the big consoles would have their start motor). My TTR-200 and T-200 have basically the same generator, but with a drum scanner mounted next to the self starting motor. As the delay lines in these organs appear to be the same, I think both scanner types show indentical capacitance values between the rotor and the stator plates. Am I correct?

Best regards!

--