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Studiomaster 800c rebuild.

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jbl_man View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jbl_man Quote  Post ReplyReply Direct Link To This Post Topic: Studiomaster 800c rebuild.
    Posted: 29 April 2010 at 12:30pm
Here is an old RSD 800C i picked up dead this week,bought as broken,so i thought would post a few photos of it being rebuilt.
Cosmetic condition was quite good,considering its 32 years old,there is a a few scratches,but nothing terrible.
 
First step was to give it a good hoover-out,and then clean it up with fine paintbrush and air-line.
 
Back panel view.
It was fairly obvious that although i bought this for spares,the condition warrants fixing it,and bringing it back to life....quick visual examination revealed a handful of old corroded 20mm fuses,and several burnt resistors....
 
This is one of the output boards..note the burnt 5.6ohm resistor,(end of screwdriver to show)..quite big these,about an inch long,so probually 5watt? Andy tells me
there is a capacitor around 0.1 connected to it with a output coil.
 
Easier to see with one of the driver boards removed.
 
A bit awkward to see,but its hidden behind the relay on the output boards...same on both channels,so will change those.
 
Will post up some more photos when parts arrive.
 
Thanks to Andy for his help.Thumbs Up
Be seeing you.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote burningbush Quote  Post ReplyReply Direct Link To This Post Posted: 29 April 2010 at 3:07pm
Fascia looks very good, better than the ebay pics showed.  Fair bit of minor corrosion on the solder, do you think that will cause problems? or do you think it will have negligible effect?
Just seen the pin board connection between boards, the green strip connector - looks like a sticky brick.
Love the lay out of the front panel.
music is the message
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TRE4U2NV Quote  Post ReplyReply Direct Link To This Post Posted: 29 April 2010 at 4:28pm
gotta luv studiomaster when fred was involvedClap
IM SO SECRETIVE BUT I CANT TELL YOU WHY
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Wrighty Quote  Post ReplyReply Direct Link To This Post Posted: 29 April 2010 at 6:10pm
The orange/brown stuff around the solder joints is just old flux - nothing to worry about. Obviously they didn't bother with (or didn't have the equipment for) cleaning PCBs back then!
ALL YOUR BASS ARE BELONG TO US.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jbl_man Quote  Post ReplyReply Direct Link To This Post Posted: 01 May 2010 at 4:15pm
Update time.
 
Broken track on one of the driver boards,had to repair a half-inch section.
 
New wire-wound resistors replaced old burnt ones.
 
 
Old output transistors were shorted on the right-hand channel..replaced with ten new RCA mj15003...quite awkward to get these,had to remove fan to gain access to mounting bolts.
Be seeing you.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote madboffin Quote  Post ReplyReply Direct Link To This Post Posted: 01 May 2010 at 6:12pm
You've probably done this anyway, but don't forget to check all emitter resistors for open circuits.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mhamplification Quote  Post ReplyReply Direct Link To This Post Posted: 01 May 2010 at 8:44pm
That looks like a nice old amp there
Should be a good usable amp when you have finished it
Were these amps reliable in use    I guess they must have been as the Froggy roadshow used them and I bet those took a right beasting in use
I remember repairing one back in the 1990`s  the metal relays  were both badly burnt so replaced them with newer plastic case ones
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Post Options Post Options   Thanks (0) Thanks(0)   Quote phildat Quote  Post ReplyReply Direct Link To This Post Posted: 06 May 2010 at 11:57pm
i have one i dont need if any one wants to make an offer...tatty case. red light doesnt light when powered up, but works fine....
Its just a ride.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jbl_man Quote  Post ReplyReply Direct Link To This Post Posted: 08 May 2010 at 12:21pm
Ok..replaced a couple of the emittor resistors (thanks for the tip madboffin!)...and....it lives!
 
Appologies for the distortion on this clip,the little camera microphone just cant cope with the levels.
 


Edited by jbl_man - 08 May 2010 at 12:25pm
Be seeing you.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote burningbush Quote  Post ReplyReply Direct Link To This Post Posted: 08 May 2010 at 12:34pm
Congratulations, job well doneClap.
What does the green light signify?
music is the message
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mhamplification Quote  Post ReplyReply Direct Link To This Post Posted: 08 May 2010 at 5:59pm
Originally posted by jbl_man jbl_man wrote:

Ok..replaced a couple of the emittor resistors (thanks for the tip madboffin!)...and....it lives!
 
Appologies for the distortion on this clip,the little camera microphone just cant cope with the levels.
 
 
Nice job you have done there Ian
I guess you must have sorted out the "Hi Tension" side as well  !!!!   Sorry couldnt resist that one
You will have to watch listen to the video to understand
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DC6ms Quote  Post ReplyReply Direct Link To This Post Posted: 08 May 2010 at 6:56pm
Bless the funk!!!
 
Saw Hi Tension live at one of the Purley All Dayers
 
DC
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