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Topics - GIMAGUITARS

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HELLO EVERYONE! I'M LOOKING FOR A PEDAL LAYOUT OF THE RED CHANNEL FROM THE RANDALL RG100ES THAT ISN'T THE "PREAMP FROM HELL" MUNKY VERSION.  I'M OKAY WITH RUNNING IT AT THE STOCK 24 VOLTS WITHOUT MODDING IT OR DROPPING VOLTAGE.  IF SOMEONE HAS THE LAYOUT FORMATTED WITH ALL CONNECTIONS NECESSARY FOR THE BUILD WITH OR WITHOUT TRUEBYPASS AND A DC JACK IT WOULD BE APPRECIATED.  SO, CHECK YOU FILES IF YOU HAVE IT AND POST IT.  THANKS ALL. 

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Hello all!  Thank you in advance to all who read, reply and assist in reviving this amp back to life.
 Let's jump right into this project.... 

I recently picked up a Marshall Lead 12 that has a volume/ output issue. 

ABOUT THE MARSHALL LEAD 12:
This amp currently sells on ebay in head or combo form from $75-$150 so please do not suggest that I just go buy one as I know it is on the verge of working. The ultimate plan is to slave the lead 12 into a power amp as it sounds (to my ears) close to a JCM800 for a solid state amp and even better with a distortion pedal (tube screamer) as most would suggest.  There is very little info online about the lead 12, combo-head conversions, and modding solid state amps.  I do have pictures of the chassis and a schematic for the 3005 and the lead 12 reverb ( I'd like to build the driver and recovery circuit and add reverb but the amp has to be working first).  This particular model was made in 1986 and its got mojo.
I'll try to be as detailed as possible to better aid those aiding me.
-The amp is 12 watt R.M.S / 8 ohm
-120v   40/60Hz  35VA
- The layout of the amp from left to right on the front is:
high input--low input--gain--volume--treble--middle--bass--line out-- power switch

A FEW NOTES ON COMMON SENSE WITH THIS AMP:
-This is an 8 ohm head and was run through an 8 ohm cab, so there's no impedence issues
-all solder joints are good/ have been re-tinned
     

SYMPTOMS:
-very low volume when plugged into external cab
-When volume knob is turned all the way up there is a semi-high pitched hum
-no noticible change when gain knob is turned

WHATS BEEN DONE/ REPLACED:
High gain (mono) input plastic like original
Low gain (stereo) input plastic like original
zener diode 9.1v 0.5a- like original
Power transistors - mj2501 and mj3001
genuine marshall volume pot.(1m) and gain pot (22k)
2 external speaker input jacks (2 x mono plastic) wired through chassis instead of hole through bottom
IC Socket added / Replaced original MC1458 with same model IC
New power cord has been rerouted through back of chassis
All electrolytic capacitors (power- 2x 2200uf/50v , c13/c15/c16 22uf/ 25v , c14 100uf/ 25v)
Pots and jacks have been sprayed with deox-it and left to dry for a few days at room temp.


THEORIES FOR MALFUNCTION/ NOTES:
-Possibly transistors which are untested (1x bc212  , 3x bc184).  BC212 is a PNP and BC184 is an NPN.  both are low power audio amplifiers.
-Also untested are 5 film capacitors (box shaped) 2 x .022 m 400, 2 x .22 k 100, 1 x .047 m 250.  Actually all the caps are untested as I don't have a capacitor meter. 
-all resistors have been tested (in circuit) and are operating within in their 5-10% range with one exception.  R4, which is a 47k ohm resistor and is reading at 18.5 k ohms after new zener diode was installed.
-there is one fuse in this amp and it hasn't blown once.
-bridge rectifier (W005) has been tested in circuit and works.
-everything else is original.
-Lighted power switch does light up


I think the problem is with the transistor(s) as the amp receives and generates power but the audio signal is not being amplified or passing through to be amplified. I have heard and read that bad potentiometers are sometimes the culprit, could this amp be the victim of malfunctioning pots? 

Thanks for checking this out and helping if you can! 

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