ADA Depot - A Forum To Support Users of ADA Amplification Gear
Non ADA Gear => Rack Gear => Topic started by: McLeanAB on August 06, 2014, 10:36:00 AM
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Hey all,
So I traded some stuff for a lovely analog old beat up Rocktron Prochorus. Old being the operative word! Had a tech friend give it a once over... a few old rotten egg smelling filter caps, and the pots were so sticky, he had to spray them and let it sit overnight... the pots were fine when the contact cleaner was still in there making all of the connections.
However, when I got it back, the pots are still scratchy and not connecting well... a touch of the knob or a twist would disconnect and reconnect... ordered some new ones from Rocktron and I'll install them this week when they arrive...
It has two modes: instrument and line level in/outs (I believe my tech said that the switch affects both in/outs, not just outs).
But, here's the issue... it works and sounds great. I put it in instrument mode, plug a guitar straight in, and it sounds amazing running direct to the mixer. Turn it off, put it in line mode, run a cab emulated line level signal that is some high gain shred tones from my ISP Theta Preamp, and it sounds killer (a bit of tone suck, but that's just old gear).
BUT, when I run a clean tone from the ISP, no cab sims (direct Alex Lifeson ala PREST/HYF), it "pops" or sounds super percussive and not in a good way. Almost as if there is an overdriven compressor. If it's doing that with the high gain sounds, it can't be heard... There is a clip light, but it doesn't come on unless I have the volume of the Theta cranked. Even at really low volumes it does this... and, in line mode, there's a bit of very light hum...
Some of the descriptions of the very few faulty Fulltone TERC (the new reissue of the Dyatronics Tri-Stereo Chorus: That Eighties Rack Chorus) seem to do this as well... I'm curious what this could possibly be? Am I hearing the millisecond delays compounding the normal percussive clean sound from the Theta, or is there something in the unit that isn't right? I'm happy to send a manual and block diagram (which says compressor, buffer, expander in the diagram), but being as how the couple of TERC's had a similar issue (popping and percussive snaps), is it something inherent to old analog chorus units? I don't think that specific problem with the TERC ever get traced down... I think replacements were shipped or there were refunds. I'd love to know if anyone has ever had something similar in any sort of vintage or new gear...
I can post clips if the descriptions are unclear...
Any and all thoughts are appreciated... my tech guy is a little stumped as well... his guess is that the input om amp could be blown, but he's not sure... he replaced it already when he cleaned the unit up, but...
I was thinking of saving up for a Shiva Audio THE WAVE if I can't get this sorted out... or just sell the bloody lovely thing as is with the new pots not installed.
Help!
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What happends if you go clean from the ISP and use the cab sims? Do you still get the pops?
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What happends if you go clean from the ISP and use the cab sims? Do you still get the pops?
It barely noticeable, but it's there... I'm guessing with all the high gain, it's just masked... if it's in line mode, with just a guitar plugged directly in, it tends to do it a bit as well... I'm guessing it's something in line mode that is faulty...
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Do you have a schematic?
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This is all I got... Trullmon fixed her up for me before I seemingly killed her...
I just replaced the old scratchy pots and they were smooth and silent with no scratches.
HOWEVER, the slowest setting on the Sweep (rate) is now double what it was before I started!! I thought maybe it was the new pot, so I carefully removed it, and put back in the old one. SAME THING!!! I am at a loss and very sad...
I'm almost ready to give it to Trullmon to salvage and sell at his leisure...
I can take pictures, but I don't know if that will help... I'll ask Matt, he might have gotten the schematic from Rocktron or Buck Waller at ISP, who designed it.
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The popping sounds like compressor to me, can you turn it off and compare ? The sweep rate change is interesting, sounds like something playing up.
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Marshall JMP,
Here's the only copy of the Prochorus schematics that Rocktron has..