This was a bear for an old guy like me but Victory! I am submitting notes
in the hope they can help someone else in the future.
Customer's original complaint was F#3 sounded kind of hollow. I found that
with only the 8' drawbar out there was no sound on that one note. Also, with
the 4' F#2 was out and with 16' F#4. It was the same on both keyboards. One
tone was not sounding. With help from the list, I learned it was tone #43
that was out. With another tip from the list, I put a clip lead from there
to a drawbar that was pushed out and had tone! So I figured, hoped that it
was just a broken wire. Well it was but what a project. I took off the
top/music rack then unbolted the keyboards. As I was advised, you need to
protect the wood sides if you going to lift the keyboards. My wife does a
bit of laminating and I had her take 2 full sheets of card stock and
laminate them. They were perfect and I used blue painters tape to hold them
in place. I removed 2 bolts on top (long screws) and 2 bolts below in front.
There are 2 more bolts in the back. Problem is the reverb tank is in the way
for one. The reverb tank is mounted on 2 metal brackets. The brackets are
easy to remove with 4 screws at the back of the cabinet. Took out the tank
and removed the bolts. There is also a small bracket under the front of the
keyboard with 2 wood screws in the rail and 2 machine screws in the base of
the lower keyboard. I removed that.
I found that I could reach under the keyboard and push it up. I got a
couple of wood blocks 4 ( 3/4"x3/4"x 9") and pushed up from underneath with
one hand on the upper keyboard and with the other pushed the block in at the
end. This is the first time I have done this so I approached this very
slowly and carefully. When you tilt up the upper keyboard you can see the
wires going to the tabs on the upper keyboard, with second wires going down
to the lower keyboard.
I ASSUMED THE TABS MATCHED THE KEYS. THEY DO NOT! I ran a new wire from
what I assumed was the correct tab to the tone but that did not fix it. I
reluctantly started cutting the cotton string bundling of the wires. I cut
as little as possible until I could follow the one wire. As I pulled it
through I could see where it was broken off. I don't think I ever would have
seen it no matter how much light I got in there or how close I looked. Once
I found it, it was obvious. I soldered my extra wire (a stranded wire) to
the tab and all is good. Of course I covered the lower keyboard with
cardboard to protect it from my solder and soldering iron.

These black wires in the bundle from the generator to the keyboards are
solid wire. If you do not lock down the generator before moving it, I
imagine it does not much time at all for those wires to begin breaking.

I hope this will help someone. It was a physically difficult repair (at
least for someone who is 70) but I am glad I was able to get it.


Rich Reid
208-861-9263

Hi John,

seven months later I'd like to ask you if you did manage to nail down the issue?

I don't suspect an oscillating PSU in the AO-28, as there are no active components within the PSU. Just passive capacitors and resistors. And if the issue were inside the preamp, the annoying thumb sounds weren't associated with the generator's rpm.

Best regards!

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This should work, the exact value is unlikely to be critical. The purpose of the resistor is to reduce power to the starter motor during the part of the start up cycle where both the start and run switches are on. You may be able to obtain a 270 ohm resistor, which is a common standard value, but if you already have a suitably rated 220 ohm to hand, I see no problem with using that. In fact, I seem to recall official Hammond advice to service engineers to short out that resistor if a faulty run switch is suspected of leaving the resistor permanently in circuit. Not, it's true to say as a permanent solution, but as a diagnostic tool. If an organ was hard to start normally, but could be started with the resistor shorted out, this would indicate a faulty run switch. Given that the factory was happy to recommend shorting the resistor out, albeit temporarily, I can't see that using a resistor only a little over 10% lower could be a problem.

Thanks, Rich. My organ is a C3, 117V
Lacking an exact 250 Ohm value or original Hammond P/N, I may choose a 220 Ohm 10W instead.

Am 12.07.2021 um 21:33 schrieb Rich Reid via groups.io <richreid01@...>:

?

Christoph,

??????????????? I have an A-100 I am working on. I checked and the one in here is 250 ohms, maybe 15 w. P/N AO-19124-15. This is a 115 volt unit. I would think 1,000 makes sense for your double voltage.

?

Rich Reid

208-861-9263

?

From: [email protected] [mailto:[email protected]] On Behalf Of Christoph
Sent: Sunday, July 11, 2021 12:49 PM
To: [email protected]
Subject: Re: [hammondzone] Starting helper resistor in A-100

?

Yes, I said that.?

—

Christoph?

?

Am 11.07.2021 um 20:39 schrieb Uwe Menrath <uwe.menrath@...>:

?Why do you need to know this resistor's value? Do you intend to re-install the original motors?

Best regards!

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Thanks, Rich. My organ is a C3, 117V
Lacking an exact 250 Ohm value or original Hammond P/N, I may choose a 220 Ohm 10W instead.

开云体育

开云体育

Yes, I said that.?

Why do you need to know this resistor's value? Do you intend to re-install the original motors?

Best regards!

117V. Thanks, Rich and Chris. 1000 Ohms for 230V makes sense. Takes into account there is higher current due to double voltage plus change in impedance due to lower frequency (50Hz).

One of the rare cases Hammond showing awareness of the presence of the 230V/50Hz world in their documentation.

—
Christoph

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I believe that R87 is 250 ohms for 117 volt organs, 1000 ohms for 234 volt versions.

Actually a chopped C3, but start- and runmotor have been dropped in bringing a modified genny with a belt driven gear ( so called German Bertram motor modification) back to stock.

They took out even the start motor and replaced the run motor with that motor gear box where the tooth belt used to wear out over the decades.

Also R87 is missing. Now the schematics for the A100 say R87 to be 250 Ohms (1000) in parens.
What now?

—
Christoph

开云体育

IS this a 220v or 110?

Rich Reid
208-861-9263

Actually a chopped C3, but start- and runmotor have been dropped in bringing a modified genny with a belt driven gear ( so called German Bertram motor modification) back to stock.

They took out even the start motor and replaced the run motor with that motor gear box where the tooth belt used to wear out over the decades.

Also R87 is missing. Now the schematics for the A100 say R87 to be 250 Ohms (1000) in parens.
What now?

—
Christoph

Hi Christoph,

it's about these connectors. And yes, you're right, I'm in search for the crimp on versions, not the PCB ones:


I'm planning to convert my wooden 760 SS Leslie into a tube powered one, with significantly increased output power. To get that typical sound not only at ear blasting levels, the organ will first drive a small PP output stage (2 x 6BX8's/ECL84's) that feeds into a resistor or a speaker impedance emulation circuitry, and from that via a master volume into the big power stage with an output power of about 180 watts. The ?iron? (PT, OT) comes from a scrapped German Dynacord Gigant amplifier, but the power tubes won't be EL34's anymore, 'cause today productions' tubes hardly can cope with 900 Vdc plate supply voltage, but Russian GU-50's instead that reportedly are beefy enough. The amp itself will sit on a Leslie 102 chassis, but there's no space for the PSU there, too. Hence the power pack with that boat anchor of a PT will sit on another chassis (from a 8022 organ), connected via an umbilical cord with the amp. And exactly for this umbilical I intend to use connectors like those in the pic.

Hansi Enzensperger from Organ Explosion, a Munich jazz trio, has conceived the idea for this project years ago.

Best regards!

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As Scott says you have to raise and tilt the manuals back for access to the terminal strip under the manuals where the wires are connected. I've come across a few UK built A-100's over the years with similar problems. Very often, it turned out that the offending terminal had not been soldered in the factory, the wires were just wrapped around the tag!

Hi all,

??????????????? I have an A-100 with a tone out. 8’ F#3 is missing. That tone is out on both manuals and 4’ on F#2 and 16’ on F#4. The tone is #43 and it is good coming out of the generator. I am thinking (hoping) a broken wire at the keyboard end. The connection at the generator end is good. I can’t see where these wires, the bundle of black wires, terminate. From the schematic they connect to the upper manual and jumper to the lower.

I have removed the top, music stand. I have unscrewed the switch plate with the drawbar assy. And tilted it up. I still can’t see where those wires connect. Do I need to completely removed the keyboards?

Any help would be greatly appreciated. I have repaired quite a few preamps and wiring problems but never removed the manuals. That looks like a large project.

thanks ??

?

Rich Reid

208-861-9263

?

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开云体育

Can you give an example which connection you mean for instance? If you mean the light nylon connectors, these are Molex and many distributors like RSS, Farnell, Reichelt, Mouser, to name a few, are carrying them.

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You must raise the manuals to access the terminal strips under them. You've done well to isolate this problem down to the connections on those terminals.

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You can get a reasonable idea of a speaker's nominal impedance by measuring it's resistance with a meter. DC resistance as measured by a meter will usually be a little lower than the impedance (about 10~20% lower). I believe that the rotosonic used as an internal Leslie in the Concorde was 8 ohms.

Thanks, Chris!

Concorde and similar power amplifier modules were rated at 35 watts @ 8 ohms. I do know that. But what I don't know is the actual impedance of a Rotosonic 9" x 6 ". If it is 16 ohms as with the reverb speakers in, say, a 251, output power is halved at about 18 watts. If it is 8 ohms, they might cope with 35 watts indeed (besides for lower frequencies, as you mentioned).

Best regards!

Hi,

does anyone know how the male and female contact pins that populated those plastic plug cases in newer Hammonds are denominated, and if there's any chance to source them as new in Germany or the EU?

Best regards!

Thanks, Chris!

Concorde and similar power amplifier modules were rated at 35 watts @ 8 ohms. I do know that. But what I don't know is the actual impedance of a Rotosonic 9" x 6 ". If it is 16 ohms as with the reverb speakers in, say, a 251, output power is halved at about 18 watts. If it is 8 ohms, they might cope with 35 watts indeed (besides for lower frequencies, as you mentioned).

Best regards!