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icon4.gif  identification and schematics [message #13069] Tue, 02 March 2010 11:11 Go to next message
ElectricRoomAmps is currently offline  ElectricRoomAmps
Messages: 8
Registered: March 2010
Location: oakland ca
Junior Member
I have two kustom amps for repair in my shop. I believe one is a 200a energizer PA with a serial # of 19937. I was able to identify it on the "67" ross catalogue on this site.

The other was a combo amp that someone made into a head unit thus devalueing it im sure. I identified this as a SC series either a 2-10sc, 4-10sc, 2-12jsc or a 2-12asc all models are same amp with different speaker options, with a serial # of 70863. I identified it in the combo amp section on this site.

I would like to get ahold of schematics for repair. The PA gets no sound whatsoever. I tested out all 6 power transistors the RCA 36892s they registered a hfe of 9 the lowest and 33 the highest. Tested them at 10 microamps and 4 volts anyone now if these are in spec or not ?


One channel blown on the guitar amp which i read on a previous post that it is probably first transistor on that channel. I would like schematic to identify transistor so I can look up specs before testing .Any help would be appreciated

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Re: identification and schematics [message #13071 is a reply to message #13069] Tue, 02 March 2010 12:54 Go to previous messageGo to next message
chicagobill
Messages: 2005
Registered: April 2003
Senior Member
Welcome to the place.

Almost all Kustom amps have a pc board number etched into the foil side. If you let us know what boards you need, we can try and supply the schematics to you.

As for the gain characteristics of the output transistors, I wouldn't worry too much about it. I've only seen one case where the gain was too low to work in a Kustom power amp.

I'd suggest starting with the power supplies in the PA head.

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Re: identification and schematics [message #13073 is a reply to message #13071] Tue, 02 March 2010 13:00 Go to previous messageGo to next message
ElectricRoomAmps is currently offline  ElectricRoomAmps
Messages: 8
Registered: March 2010
Location: oakland ca
Junior Member
i will check out power supply and find board numbers, thanks

brian@electricroomamps.com

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Re: identification and schematics [message #13074 is a reply to message #13069] Tue, 02 March 2010 13:36 Go to previous messageGo to next message
ElectricRoomAmps is currently offline  ElectricRoomAmps
Messages: 8
Registered: March 2010
Location: oakland ca
Junior Member
I tested power supply. I got 57.4 VAC off transformer and 76.4vdc off of the caps without powertsansisters in circuit. I believe these are proper voltages based on all the other posts I read.

I also tested two rca 36892s in the k150sc series guitar amp which i know were good and got comparable results so I believe they are all good.

Will begin to identify boards in amp for futher classification.

Thanks to chicagobill for info and assist.

brian@electricroomamps

brian@electricroomamps.com

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Re: identification and schematics [message #13075 is a reply to message #13069] Tue, 02 March 2010 14:22 Go to previous messageGo to next message
ElectricRoomAmps is currently offline  ElectricRoomAmps
Messages: 8
Registered: March 2010
Location: oakland ca
Junior Member
I got board numbers off of pc's. The first channel is labeled "ROSS PC 102" I didn't pull channels 2-3 they are all identical.
Preamp board is labeled "ROSS PC 802"
Two small boards off of preamp board are labeled "ROSS PC 602" and "ROSS PC 502"
Poweramp board is labeled "ROSS PC 702"

Any help with schematics would be greatly appreciated.

Thanks

brian@electricroomamps.com

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Re: identification and schematics [message #13077 is a reply to message #13069] Tue, 02 March 2010 19:08 Go to previous messageGo to next message
pleat is currently offline  pleat
Messages: 1453
Registered: June 2004
Location: Belding, Mi
Senior Member
Welcome to the site. On the guitar amp that you suggested is either a SC 2x10, 4x10 or 2x12. The SC 2x10 and 4x10 are 22 inches wide. The SC2x12 is wider and will have a different pre amp board numbers for the wider 2x12 amp.
pleat

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Re: identification and schematics [message #13082 is a reply to message #13069] Wed, 03 March 2010 17:39 Go to previous messageGo to next message
chicagobill
Messages: 2005
Registered: April 2003
Senior Member
I have sent you the schematics that I have.

As I recall the PC802 is the reverb/mixer board. It shouldn't be too hard to figure out.

There should be + and - 34vdc at the filter caps.
The two regulator boards will supply + and - 23vdc for the preamp and mixer boards.

Start by testing the PC702 power amp board. Is the speaker fuse ok? Is there any voltage on the output?

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Re: identification and schematics [message #13085 is a reply to message #13077] Wed, 03 March 2010 19:55 Go to previous messageGo to next message
ElectricRoomAmps is currently offline  ElectricRoomAmps
Messages: 8
Registered: March 2010
Location: oakland ca
Junior Member
The guitar amp is 22 inches wide so it must be a 2x10 or a 4x10.
I have fully taken it apart and identified boards on it.
PC 5032 REV 1
PC 1500
PC 1400 REV 1

PC 1500 is board with problem and the 1 I need the most.
Thanks for the help!

brian@electricroomamps.com

[Updated on: Wed, 03 March 2010 20:58]

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Re: identification and schematics [message #13086 is a reply to message #13082] Wed, 03 March 2010 20:04 Go to previous messageGo to next message
ElectricRoomAmps is currently offline  ElectricRoomAmps
Messages: 8
Registered: March 2010
Location: oakland ca
Junior Member
Update on mixer! After testing out power transistors, checking power supply voltages and a thorough cleaning of fiftysome years of dust, I tested it out for the first time since picking it up.
Channel 1 and 3 are fine. Channel 2 and 4 are blown out! 2 more than 4 because a little of the signal gets through at full volume. My pal didnt even know it was a mixer, was using it as aguitar amp and didnt know how to operate all channels. But they did kill at least 1 channel or possibly both, who knows. Temporarilly returned it so he could use it till I get schemos, which i think I might have now and need to print.

Thanks all for replying and sending schemos.

brian@electricroomamps.com

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Re: identification and schematics [message #13088 is a reply to message #13069] Thu, 04 March 2010 03:24 Go to previous message
ElectricRoomAmps is currently offline  ElectricRoomAmps
Messages: 8
Registered: March 2010
Location: oakland ca
Junior Member
I fixed the k150 sc series guitar amp! The first transistor was fried (had an hfe of 11 when shouldve been between 1 and 3hundred) just as suspected after reding earlier posts. It had already been replaced once with a 2n3904 and I had 1 in my shop, didnt even have to go by parts. I would like to thank everybody who helped out with schemos and info and troubleshooting tips.

Anyone near Oakland, CA need amps repaired look me up....

brian@electricroomamps.com

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