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Thanks Tony,

Update: I got the bias down to around 50mA and the DC offset down to around -50mV.
It runs a bit hot but not as hot as it did before the rebuild.
The sound is great and there's zero ...

Update:

I swapped the position of two 2N3055 in the bass amp and the DC offset came down from -150mV to -58mV
Interesting.

One more question:
The over all specs for the Leslie 760 state that ...

Thanks for the great explanation.
Now I understand why the bottom resistors are hotter than the rest.

I still cant find, or understand whats causing the DC offset.
There aren't that many componen ...

Ok. Makes sense.
I've seen that on tube amps.

I tried to trace the offset back from the speaker.
It appears in the B- 42v right after R86 (at the base of Q14)
Does this mean that Q14 is pulling ...

Thanks Stephen,

I'll try that.

What I don't understand is - why the bass amp has the speaker as part of the feedback loop and the Treble amp doesn't?
I'm trying to rule this out as part of ...

Update:
I’m getting closer and not closer.

Emitter bias down to 35mV both amps. Good enough.
I re-flowed some solder joints around various ground points.
No clue why it came down.

Anyway it ...

Excellent.
Makes sense.
I will see if I can find a short / partial short after point R.
I wonder if the blocking caps in the feedback loop are going. That could cause the offset also right?

When ...

Thanks Quentin for all the great info.

I do have a scope and a signal generator.
The input capacitor on the crossover was bad.
Replaced it and it's all working again.

Now I'm back where I star ...

(I was looking at the wrong part, those TO220 resistors are $11. Still too high though)

Thanks Quentin,

I looked those up on Mouser.
$63 a piece. I don't think I'll go that route.

Update: I got the DC offset on the treble speaker way down to 20mV. Bass side is still around 60mV. ...

Thanks Stephen,

Agreed it has to be something in that final stage.

The amp was fairly noisy and had a good amount of hum when I got it - thus the rebuild. Now it's quiet, hum is gone, and it sou ...

Thanks Stephen,

I also have a Leslie Combo Pre-amp II so I can run anything into it.

I'll leave the resistors stock specs.

I did let it run for a couple hours and it seems stable.
They just ...

Thanks for the quick reply Donny,

The resistors are new and therefor smell a bit when hot , but no discoloration and no smoke (yet).

Maybe I'll let it run a while and see if the smell lessens? ...

Solid state amp question:

Leslie 760 rebuild: It was running hot.
I replaced all the electrolytic capacitors in the power supply and amp boards.
Also replaced the power resistors on the amp boa ...

Thanks Jeff,

Update: I installed a small 12v power supply and a relay. Works good. No more 120v to the foot switch.
I still wish I knew what circuit is buried in the epoxy module but I guess it wi ...

Thanks Bill,
I had a Space Echo also. What a sound.

I'm leaning towards the 12v relay / wall wart solution.

Thanks Bill,
I was posting at the same time.
Makes sense - no transformer.

Thanks George,
The extra symbol is the pilot lamp for "motor on".

The motor is a shaded pole AC motor.

Here's a picture showing the module buried in epoxy and a big transistor on a he ...

I have this old oddball Oliver Orbital Power Projector. (sort of a Leslie upper horn)
I found the overall schematic but the schematic for the motor speed control module is nowhere to be found. The p ...

I found one.
You can close this.
Thanks everyone.

Nice. I appreciate all the offers but I'm only looking for the Midiverb II.
I might end up getting one from reverb or ebay but I thought I'd try here first as it's more enjoyable to buy and sell her ...

Thanks David,
I appreciate the offer.
That is close (by a difference of I)
But I am only seeking the Midiverb II.

Like this:

https://bb.steelguitarforum.com/userpix2203/6469_alesismidiverbii ...

Thanks Raybob.

I'm looking specifically for the Midiverb II.
I had one back in the early 90's lost track of it and then got another one about 10 years ago and eventually sold it. There is one spec ...

Looking for an Alesis Midiverb II.

Thanks,

Open to offers.

Author	Message
Topic: Solid State Amp runs hot
Ivan Funk Replies: 25 Views: 4186	Forum Section: Electronics Posted: 21 Jan 2024 12:37 pm Subject: Solid State Amp runs hot
Ivan Funk Replies: 25 Views: 4186	Thanks Tony, Update: I got the bias down to around 50mA and the DC offset down to around -50mV. It runs a bit hot but not as hot as it did before the rebuild. The sound is great and there's zero ...
Topic: Solid State Amp runs hot
Ivan Funk Replies: 25 Views: 4186	Forum Section: Electronics Posted: 10 Jan 2024 12:04 pm Subject: Solid State Amp runs hot
Ivan Funk Replies: 25 Views: 4186	Update: I swapped the position of two 2N3055 in the bass amp and the DC offset came down from -150mV to -58mV Interesting. One more question: The over all specs for the Leslie 760 state that ...
Topic: Solid State Amp runs hot
Ivan Funk Replies: 25 Views: 4186	Forum Section: Electronics Posted: 9 Jan 2024 1:19 pm Subject: Solid State Amp runs hot
Ivan Funk Replies: 25 Views: 4186	Thanks for the great explanation. Now I understand why the bottom resistors are hotter than the rest. I still cant find, or understand whats causing the DC offset. There aren't that many componen ...
Topic: Solid State Amp runs hot
Ivan Funk Replies: 25 Views: 4186	Forum Section: Electronics Posted: 9 Jan 2024 10:39 am Subject: Solid State Amp runs hot
Ivan Funk Replies: 25 Views: 4186	Ok. Makes sense. I've seen that on tube amps. I tried to trace the offset back from the speaker. It appears in the B- 42v right after R86 (at the base of Q14) Does this mean that Q14 is pulling ...
Topic: Solid State Amp runs hot
Ivan Funk Replies: 25 Views: 4186	Forum Section: Electronics Posted: 8 Jan 2024 10:42 pm Subject: Solid State Amp runs hot
Ivan Funk Replies: 25 Views: 4186	Thanks Stephen, I'll try that. What I don't understand is - why the bass amp has the speaker as part of the feedback loop and the Treble amp doesn't? I'm trying to rule this out as part of ...
Topic: Solid State Amp runs hot
Ivan Funk Replies: 25 Views: 4186	Forum Section: Electronics Posted: 8 Jan 2024 6:32 pm Subject: Solid State Amp runs hot
Ivan Funk Replies: 25 Views: 4186	Update: I’m getting closer and not closer. Emitter bias down to 35mV both amps. Good enough. I re-flowed some solder joints around various ground points. No clue why it came down. Anyway it ...
Topic: Solid State Amp runs hot
Ivan Funk Replies: 25 Views: 4186	Forum Section: Electronics Posted: 8 Jan 2024 11:22 am Subject: Solid State Amp runs hot
Ivan Funk Replies: 25 Views: 4186	Excellent. Makes sense. I will see if I can find a short / partial short after point R. I wonder if the blocking caps in the feedback loop are going. That could cause the offset also right? When ...
Topic: Solid State Amp runs hot
Ivan Funk Replies: 25 Views: 4186	Forum Section: Electronics Posted: 8 Jan 2024 1:15 am Subject: Solid State Amp runs hot
Ivan Funk Replies: 25 Views: 4186	Thanks Quentin for all the great info. I do have a scope and a signal generator. The input capacitor on the crossover was bad. Replaced it and it's all working again. Now I'm back where I star ...
Topic: Solid State Amp runs hot
Ivan Funk Replies: 25 Views: 4186	Forum Section: Electronics Posted: 7 Jan 2024 4:10 pm Subject: Solid State Amp runs hot
Ivan Funk Replies: 25 Views: 4186	(I was looking at the wrong part, those TO220 resistors are $11. Still too high though)
Topic: Solid State Amp runs hot
Ivan Funk Replies: 25 Views: 4186	Forum Section: Electronics Posted: 7 Jan 2024 4:07 pm Subject: Solid State Amp runs hot
Ivan Funk Replies: 25 Views: 4186	Thanks Quentin, I looked those up on Mouser. $63 a piece. I don't think I'll go that route. Update: I got the DC offset on the treble speaker way down to 20mV. Bass side is still around 60mV. ...
Topic: Solid State Amp runs hot
Ivan Funk Replies: 25 Views: 4186	Forum Section: Electronics Posted: 6 Jan 2024 10:40 pm Subject: Solid State Amp runs hot
Ivan Funk Replies: 25 Views: 4186	Thanks Stephen, Agreed it has to be something in that final stage. The amp was fairly noisy and had a good amount of hum when I got it - thus the rebuild. Now it's quiet, hum is gone, and it sou ...
Topic: Solid State Amp runs hot
Ivan Funk Replies: 25 Views: 4186	Forum Section: Electronics Posted: 6 Jan 2024 3:46 pm Subject: Solid State Amp runs hot
Ivan Funk Replies: 25 Views: 4186	Thanks Stephen, I also have a Leslie Combo Pre-amp II so I can run anything into it. I'll leave the resistors stock specs. I did let it run for a couple hours and it seems stable. They just ...
Topic: Solid State Amp runs hot
Ivan Funk Replies: 25 Views: 4186	Forum Section: Electronics Posted: 6 Jan 2024 12:09 pm Subject: Solid State Amp runs hot
Ivan Funk Replies: 25 Views: 4186	Thanks for the quick reply Donny, The resistors are new and therefor smell a bit when hot , but no discoloration and no smoke (yet). Maybe I'll let it run a while and see if the smell lessens? ...
Topic: Solid State Amp runs hot
Ivan Funk Replies: 25 Views: 4186	Forum Section: Electronics Posted: 6 Jan 2024 11:27 am Subject: Solid State Amp runs hot
Ivan Funk Replies: 25 Views: 4186	Solid state amp question: Leslie 760 rebuild: It was running hot. I replaced all the electrolytic capacitors in the power supply and amp boards. Also replaced the power resistors on the amp boa ...
Topic: Old Rotating Speaker circuit puzzle
Ivan Funk Replies: 8 Views: 1194	Forum Section: Electronics Posted: 24 Dec 2023 8:37 pm Subject: Old Rotating Speaker circuit puzzle
Ivan Funk Replies: 8 Views: 1194	Thanks Jeff, Update: I installed a small 12v power supply and a relay. Works good. No more 120v to the foot switch. I still wish I knew what circuit is buried in the epoxy module but I guess it wi ...
Topic: Old Rotating Speaker circuit puzzle
Ivan Funk Replies: 8 Views: 1194	Forum Section: Electronics Posted: 24 Dec 2023 11:11 am Subject: Old Rotating Speaker circuit puzzle
Ivan Funk Replies: 8 Views: 1194	Thanks Bill, I had a Space Echo also. What a sound. I'm leaning towards the 12v relay / wall wart solution.
Topic: Old Rotating Speaker circuit puzzle
Ivan Funk Replies: 8 Views: 1194	Forum Section: Electronics Posted: 23 Dec 2023 6:36 pm Subject: Old Rotating Speaker circuit puzzle
Ivan Funk Replies: 8 Views: 1194	Thanks Bill, I was posting at the same time. Makes sense - no transformer.
Topic: Old Rotating Speaker circuit puzzle
Ivan Funk Replies: 8 Views: 1194	Forum Section: Electronics Posted: 23 Dec 2023 6:35 pm Subject: Old Rotating Speaker circuit puzzle
Ivan Funk Replies: 8 Views: 1194	Thanks George, The extra symbol is the pilot lamp for "motor on". The motor is a shaded pole AC motor. Here's a picture showing the module buried in epoxy and a big transistor on a he ...
Topic: Old Rotating Speaker circuit puzzle
Ivan Funk Replies: 8 Views: 1194	Forum Section: Electronics Posted: 22 Dec 2023 12:45 pm Subject: Old Rotating Speaker circuit puzzle
Ivan Funk Replies: 8 Views: 1194	I have this old oddball Oliver Orbital Power Projector. (sort of a Leslie upper horn) I found the overall schematic but the schematic for the motor speed control module is nowhere to be found. The p ...
Topic: Alesis Midiverb II
Ivan Funk Replies: 10 Views: 1812	Forum Section: Wanted To Buy Posted: 1 Nov 2023 4:45 pm Subject: Alesis Midiverb II
Ivan Funk Replies: 10 Views: 1812	I found one. You can close this. Thanks everyone.
Topic: Alesis Midiverb II
Ivan Funk Replies: 10 Views: 1812	Forum Section: Wanted To Buy Posted: 26 Oct 2023 7:39 pm Subject: Alesis Midiverb II
Ivan Funk Replies: 10 Views: 1812	Nice. I appreciate all the offers but I'm only looking for the Midiverb II. I might end up getting one from reverb or ebay but I thought I'd try here first as it's more enjoyable to buy and sell her ...
Topic: Alesis Midiverb II
Ivan Funk Replies: 10 Views: 1812	Forum Section: Wanted To Buy Posted: 25 Oct 2023 5:53 pm Subject: Alesis Midiverb II
Ivan Funk Replies: 10 Views: 1812	Thanks David, I appreciate the offer. That is close (by a difference of I) But I am only seeking the Midiverb II. Like this: https://bb.steelguitarforum.com/userpix2203/6469_alesismidiverbii ...
Topic: Alesis Midiverb II
Ivan Funk Replies: 10 Views: 1812	Forum Section: Wanted To Buy Posted: 25 Oct 2023 11:58 am Subject: Alesis Midiverb II
Ivan Funk Replies: 10 Views: 1812	Thanks Raybob. I'm looking specifically for the Midiverb II. I had one back in the early 90's lost track of it and then got another one about 10 years ago and eventually sold it. There is one spec ...
Topic: Alesis Midiverb II
Ivan Funk Replies: 10 Views: 1812	Forum Section: Wanted To Buy Posted: 24 Oct 2023 4:03 pm Subject: Alesis Midiverb II
Ivan Funk Replies: 10 Views: 1812	Looking for an Alesis Midiverb II. Thanks,
Topic: Boss DD-200
Ivan Funk Replies: 1 Views: 1948	Forum Section: For Sale: Amps and Accessories Posted: 6 Sep 2023 6:41 am Subject: Boss DD-200
Ivan Funk Replies: 1 Views: 1948	Open to offers.