Seeburg SHP-1 Amp Driver Board questions

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Topic author
tonily
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Seeburg SHP-1 Amp Driver Board questions

by tonily » Thu Feb 16, 2012 9:44 pm

Perhaps someone would be able to enlighten me. Hopefully I just finished repairing an SHP-1 amplifier with an early verion Driver Board (319295-A) which had the common problems on the right Channel (burnt R75 and R76...fried Q16..and damaged Q17 and Q18) I recapped it, checked for off value resistors changed all Q12, 13, 14, 22, 23, 24, All four output transistors, cr51109 and cr51110 Also Q11 (under heat-sink)etc etc. Checked the Bias pots both at just under 3K and responsive...which I brought to the minimum resistance and connected the speakers. Connected it through the jig with a 75w bulb and it has been cooking for over an hour..all is cool on both channels except for q14 and Q24 at 102F.. compared to the rest of the components at 83-84F

Here are my questions:
After all was done,
1-) Test (g) and (h) for the Left channel (Which wasn't the fried channel) gives me 97-99 ohms according to Tony Miller's SHP Amp book (which I understand to be tested at the Collector of Q16 and Q26 instead of Emitter as printed in the book) RIGHT CHANNEL tests under .5 ohm as per test (e) and (f) at collector of Q15 and Q25 What am I missing?

2-) The Schematic shows C49 and C64 as .022uF....the unit had .047uf/100v when I got it... and the parts list on the schematic shows 1uF tantalum at 35v...Which one is correct?


Ron Rich
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Re: Seeburg SHP-1 Amp Driver Board questions

by Ron Rich » Fri Feb 17, 2012 2:28 am

Tonily,
I have never temp. tested q14/24, but I recall that they ran a little warm--I think that's "normal"--
Can't answer on the tests, as I have never used them--
C-49/64 were changed to .22 in the later -A boards--to the tant. in the -B boards ( along with several other changes).
Most important--are the jumpers installed across the plug-- Is R-75/76--98/99 at least a flame proof type resistor ? Is the space for C-46 blank ( It should not be filled--that cap MUST be moved directly across the leads of the driver).
Ron Rich


Topic author
tonily
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Posts: 29
Joined: Sun Jun 27, 2010 1:00 pm
Location: Myrtle Beach SC

Re: Seeburg SHP-1 Amp Driver Board questions

by tonily » Fri Feb 17, 2012 2:22 pm

Ron,
Thanks for your reply.
Yes, jumpers are in place. Already there when I got the Amp. The burnt resistors looked like carbon 1/2W though.

Resistors I used are radio shack 1W metal oxide (raised 1/4 inch off the board). I live in a small town and RS is as good as it gets. If necessary, I plan to order the flame-proof ones. I was trying to avoid the extra $4- or so for shipping and handling just for a couple of resistors.

C-46 is in its original location (middle of the board) I also noticed that Left channel c-61 is next to Q-26...I will move it directly across the driver leads (Q-16 between E and B) as you suggested ...If it is not too much to ask could you elaborate on the reason for moving it to the driver leads?

Once again, thanks for your time and insight!
Tonily


Ron Rich
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Re: Seeburg SHP-1 Amp Driver Board questions

by Ron Rich » Fri Feb 17, 2012 6:42 pm

Tonily,
The Rat Shack MO resistors should do it---
C-46 was moved due to "oscillation" problems in that location( "electrically" it is the same spot)--the other one is OK where it is--
Ron Rich


Topic author
tonily
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Posts: 29
Joined: Sun Jun 27, 2010 1:00 pm
Location: Myrtle Beach SC

Re: Seeburg SHP-1 Amp Driver Board questions

by tonily » Fri Feb 17, 2012 7:36 pm

Ron,

Once again thanks! for taking the time to help out.

Tonily


Topic author
tonily
Regular Member
Posts: 29
Joined: Sun Jun 27, 2010 1:00 pm
Location: Myrtle Beach SC

Re: Seeburg SHP-1 Amp Driver Board questions

by tonily » Thu Aug 07, 2014 1:38 am

Here I am 2.5 years later. Now I need to replace both Bias pots on SHP-1 as they are faulty...Merely taping on the amp chassis makes them unstable...Question is, does anyone know where buy those 3.3k pots....before disconnecting I adjusted both channels to just under 1.5V at the drivers Bases, left the meters connected and tapped on the chassis near the pots and there was bias voltage variations.
Tried removing the one wire and taking measurements but it fluctuates even with minimal pot leg movement cause by the test lead (+/- 40 to 60 ohms).... Question #2, does 450 ohm or so sounds right for fixed resistors....

Thanks!


Ron Rich
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Posts: 8193
Joined: Sun May 06, 2007 11:31 pm
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Re: Seeburg SHP-1 Amp Driver Board questions

by Ron Rich » Thu Aug 07, 2014 4:56 am

Tonily,
Use Deoxit 5, on the pots--set, and GLUE them--no more problems--
Ron Rich

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