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#31
10-30-2014, 09:30 AM
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Thanks for the relply. The new one definitely is a 4EB2C1B just as you mentioned. From what my research found that was the right one too.
Also thanks for explaining that ground wire issue. That was the only thing that really wasn't making much sense to me ( except why I still have no reverb of course). I'm gonna try cleaning everything really well one more time and making sure all of the connections are sound and seeing it that'll do it with the small amount of tinkering I've done. If that doesn't work I'm guessing there's a loose connection somewhere that I have to me missing, probably somewhere signal being sent to the tank. Thanks for all the help again guys. 
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#32
10-30-2014, 09:44 AM
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Also something I didn't check. The amplifier works fine just no reverb, so could it be that there is an issue getting the signal from the amp to the reverb drive? That seems to make sense as to why I would get some noise when I bump it but nothing when it is strummed.
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#33
10-30-2014, 10:18 AM
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Quote:
__________________
Warren My website: http://draudio56.wix.com/warren-bendler "It's hard...calming the Beatle inside of me."
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#34
10-30-2014, 01:30 PM
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From the "In for a penny, in for a pound" club, if you can't gt a scope, you could build Doug Hoffman's Amp Probe:
http://el34world.com/Hoffman/tools.htm It's near the bottom of the page. It's essentially a multimeter probe with a .1uF/630V cap soldered between the probe and the hot lead of a guitar cable. The ground of the cable clips to the amp chassis. The other end of the 1/4" cable is a standard guitar plug and plugs into a small "listening amp". You would then touch the probe to the collector and emitter of each transistor, and if they are working properly a signal ought to be amplified by the small amp (you have to have a signal into the Peavey, of course). The problem with having no drive signal is that it could be the .1uF input choke cap to the circuit, the transistors, or one of the caps in the reverb circuit (I would doubt that the resistors are faulty, but it's always a possibility). Another VERY likely culprit would be a faulty solder joint on the bottom of the board. If a fault was bad enough to prevent just one element in the circuit from working, you'd have little or no reverb. You'd need to pull the board and flip it to check them. Good Luck, Bill. PS: If you think that's bad, just try to service a new amp with surface-mount components. Us Ancients need a magnifying glass just to see the part! 
Last edited by BTF; 10-30-2014 at 01:35 PM.
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#35
10-30-2014, 04:28 PM
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My eyes definitely aren't the best either. I'd want nothing to do with those!
As for my issue. I just reversed the wires that mount to the board from the RCA jacks. Still no working reverb, but man just touching that tank sends a massive reverb through the speaker.much more prevelant than before. Any ideas what that would mean? I'm guessing they were right before. Like you pointed out, I'm starting to expect a capacitor either in the drive circuit or going to the circuit. I tested the tansisitors using the diode function on my multimeter and they all seem to function as expected. I'm kinda confused by the schematic on where the input from the amp meets the drive circuit though. Another day another experience!
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#36
10-31-2014, 04:20 AM
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Forgive the lateness of my reply! Long day...
If the take-up circuit is working correctly- which apparently it is now, touching the pan roughly should create a massive crashing reverb sound. The tank when in the circuit is very sensitive to vibration since the small guitar signal alone will cause the springs to vibrate. Touching the pan obviously is many more times as disruptive. It sounds like the recovery circuit is working correctly. Perhaps someone reversed the connections. As I said, in a properly working recovery stage, the pan ought to make havoc when you shake it. As to the Drive circuit, if you look at the Master control on the schematic posted for the Artist, from the center out of the Master, the signal splits between a 4.7K resistor and a 10K resistor (we'll call it R1). The 4.7K leads to the .1uF Drive circuit input where it enters the first 3904. The pan needs a good drive current, so the signal leaves the first 3904 and enters the second 3904. The emitter of the second 3904 is connected via a 2.2k resistor to the input transducer of the pan. The resultant fluctuating AC signal voltage across the transducer coil drives the reverb input. If that 2uF cap at the junction of the 2-10K resistors at the first 3904 were bad, you would have drive problems. You'd know if the cap were bad if the voltage at the the 2-10K junctions (1.5VDC) was much lower than the schematic shows, or showed a short to ground. If the .1uF input cap was defective, you'd could tell by bridging it with a known good one, but it appears to be a box cap, and you probably can't get to the leads from the top of the board. The signal returns from the pan to drive the recovery circuit, and then proceeds through the Reverb mixing pot through a 10K resistor to the other end of the 10K resistor (R1) where the signal first split from the Master (that 10K resistor -R1- is the summing or mixing resistor). The signal at that point now has both dry signal from the other side of the 10K summing resistor, AND whatever amount of reverb you dial in from the Reverb control. I think I would leave the recovery circuit in the position where the pan makes the loudest noise and focus now on the Drive circuit. In that simple circuit, I would suspect either the 3904s or the 2 caps in the circuit, the .1uF and the 2uF at the base of the two 10K resistor junctions. Also, a faulty solder joint in that area would cause problems. Sorry to prattle, hope this helps! Good Luck. Last edited by BTF; 10-31-2014 at 05:03 AM. Reason: connection disrupted.
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