stevem Messages: 4738 Registered: June 2004 Location: NY
Senior Member
you need to pull that board off the face of the amp ,unsolder that pot and check to see if it's open resistance wise from leg to leg,and also check the board in that area for bad solder connections.
bpmadsx Messages: 30 Registered: December 2014 Location: Jenkins,KY
Member
OK will do other than that the right channel is loud , the left channel is really low and dirty
The only Transistors I have right now are S9013 and MPSA06 Will either of these work to replace some of the previous owners horrible fix attempts thanks. There are at least 2 of the original Transistors SE4002 I believe that were changed
bpmadsx Messages: 30 Registered: December 2014 Location: Jenkins,KY
Member
Thanks man I replaced the Pot and problem solved and also touched up some solder joints just for good measure the Right side is VERY LOUD and i've never heard one of these amps before in person so I have no idea what they are supposed to sound like but this thing For Sure has that late 60's early 70's Sound going on Straight CCR haha I like it . Now I just have to get the Left Side Working the High and Low on the Right works the Treble and Bass, and Volume on the Preamp Pc1400 are working. Every now and again the sounds cuts out but if I play a chord a little hard it kicks back in, Gotta line that out. Also I have to get the left side working which on Pc1500 from the looks of it the High and Low on the left only work very low volume and only when the Treble Pot is pulled out.
stevem Messages: 4738 Registered: June 2004 Location: NY
Senior Member
The s9013 would work if it was rated for 3 times the mill watt level and if you could solder it in, but good old 2n3904 transistors that can still be had at radio shack will sub for the se4002 just fine!
bpmadsx Messages: 30 Registered: December 2014 Location: Jenkins,KY
Member
stevem wrote on Tue, 16 December 2014 13:28
The s9013 would work if it was rated for 3 times the mill watt level and if you could solder it in, but good old 2n3904 transistors that can still be had at radio shack will sub for the se4002 just fine!
The reason I only have those Transistors is because I primarily work on Car Audio Amplifiers.
bpmadsx Messages: 30 Registered: December 2014 Location: Jenkins,KY
Member
I noticed the Big Box style im guessing Ceramic Resistor 6849 PW5A right above the Intensity Pot looks brown under it on both sides of the board and it looks like it might have been changed as the solder looks shiny on it. The Value it reads is 200 ohm 10% I have noticed all others like it read 1 ohm 10%, is this resistor Correct or was it replaced with the improper resistor Thanks.
The 1 ohm resistors are the ballast or emitter resistors for the power output transistors. The 200 ohm one is the voltage dropping resistor for the pilot lamp. It is supposed to drop the 40 volts from the power supply down to 28 volts for the pilot lamp. Sometimes people will put a #47 lamp in there and will cause the resistor to get hotter than normal. This will turn the pc board brown from the heat.
stevem Messages: 4738 Registered: June 2004 Location: NY
Senior Member
The symptom of signal drop out many times is due to a poor connection, so did you check that board and treble pot area for that yet like I posted about?
bpmadsx Messages: 30 Registered: December 2014 Location: Jenkins,KY
Member
Yes I replaced the Pot, that problem has been resolved.
Chicagobill im not sure what light is in there, however I have it disconnected right now because when I hook the wires to the Pilot Light it causes the amp to
start a hum that increases in loudness until its turned off when the pilot light is hooked up via the black and green wires.
bpmadsx Messages: 30 Registered: December 2014 Location: Jenkins,KY
Member
stevem wrote on Wed, 17 December 2014 06:10
The symptom of signal drop out many times is due to a poor connection, so did you check that board and treble pot area for that yet like I posted about?
I replaced that treble pot the treble pot that affects the left channel is the other treble pot on the left side pc1500 board I replaced the treble on the preamp that fixed the hum when touching that treble
It sounds like you need to remove the other board and resolder whatever is loose there as well. That should fix the signal cutting in and out.
Remove the bulb from the holder and see if there is a number or voltage rating stamped or printed on the base of the bulb. The correct bulb is a #1829.
bpmadsx Messages: 30 Registered: December 2014 Location: Jenkins,KY
Member
chicagobill wrote on Wed, 17 December 2014 15:23
It sounds like you need to remove the other board and resolder whatever is loose there as well. That should fix the signal cutting in and out.
Remove the bulb from the holder and see if there is a number or voltage rating stamped or printed on the base of the bulb. The correct bulb is a #1829.
Bulb in the amp right now is a 1847 Chicagobill
also i have touched up quite a bit of original soldering, and double checked for loose connections on Pc1400, pc1500, and Pc900
bpmadsx Messages: 30 Registered: December 2014 Location: Jenkins,KY
Member
my biggest problem right now is the left channel is out unless the treble on that side is pulled out , the push pull pot.
and other than the signal cutting out sometimes, the right channel is loud, but is also kind of dirty sounding, scratchy if you will sometimes, and If I turn the volume up its worse.
bpmadsx Messages: 30 Registered: December 2014 Location: Jenkins,KY
Member
bpmadsx wrote on Wed, 17 December 2014 16:39
my biggest problem right now is the left channel is out unless the treble on that side is pulled out , the push pull pot.
and other than the signal cutting out sometimes, the right channel is loud, but is also kind of dirty sounding, scratchy if you will sometimes, and If I turn the volume up its worse.
Do I need to replace the tantalum caps, if so what with can I use new type Capacitors with the striped positive. I'm looking all over locally for 33uf 15v caps as the Orange tantalum caps say 33-15 which I am guessing is 33uf, 15v caps , I do have some 16v caps but they are 47uf. If those will work I have enough to replace them all.
I don't know about the transistors which ones to replace and which ones to leave alone.
This is my 2nd guitar amp repair, and my first of which is anywhere near this age. I am not used to these older parts and crossing them over and what to look for I am really excited and interested in these amps and if I can repair it I might even start collecting them. Thank You to Chicagobill and SteveM for all their help so far.
If either of you could PM any other way I could contact you with photos or even videos of what the amp is doing you might see or hear something, and we Could communicate faster I love this forum but am and in bad need of someone knowledgeable about these old amps.
stevem Messages: 4738 Registered: June 2004 Location: NY
Senior Member
Unsolder that treble pot from the board and confirm that all 3 legs test ok and are not open.
Next look at the pc1500 schematic in this sites tech section and then pull out transistor q1521 and q1522 and prove out those.
I do not really see any electrolytic caps in that part of the circuit that will make for you issue you are having with that channel!