Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: LooseChange on October 29, 2010, 06:59:38 am
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I've got a Crate G-50H on the bench. It's a two channel, high gain 50 watter with four 6V6's. Not a bad sounding metal amp. The owner relabeled the front to say "2ndRATE".
I needed to pull the PC board to fix some jacks and add an IEC.
I reassembled the amp and the thing does not make a sound except when I jiggle the amp... I found I had to screw the Octal tube clamps in to ground the cathodes of the power tubes.
Great engineering Crate! You guys love service techs.
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Well, isn't that special???
Cheers,
Chip
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Sounds like every PCB amp.They often have ONE ground point for the entire PC board.And a poor one at that.
Like a Marshall TSL401.The jacks get loose on the rear panel and the switching circuit looses it's ground and stops working.Nice engineering.
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This amp has three ground points on the PC board plus the four grounds on the tube sockets.
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They didn't bother using some loctite, washer and nut?
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Most are fine from the factory,it's just when they vibrate or get worked on that they start acting up.
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I've got a Crate G-50H on the bench. It's a two channel, high gain 50 watter with four 6V6's. Not a bad sounding metal amp. The owner relabeled the front to say "2ndRATE".
I needed to pull the PC board to fix some jacks and add an IEC.
I reassembled the amp and the thing does not make a sound except when I jiggle the amp... I found I had to screw the Octal tube clamps in to ground the cathodes of the power tubes.
Great engineering Crate! You guys love service techs.
I had a Crate G1600XL for a while that I got for free off CL because both of the input and both of the output jacks were flaky and so were the input jacks on the 4x12 cabinet. The jacks were basically coming off the circuit boards and the solder joints were failing. What a crappy design. You aren't mistaken in saying they love service techs because they are basically guaranteed to fail with much of any use. The guy who had it thought the speakers and/or amp were blown out.
Sadly, after having that amp apart I noticed a lot of other amps from other makers use the same kind of crappy plastic "Cliff" PCB mounted jacks. Glad most of my stuff is vintage with panel mounted jacks. FWIW, I ended up removing and throwing out the Cliff jacks and replacing them with switchcraft style panel mount jacks with short jumper wires to the PCB so there would be some flex and the solder joints wouldn't break again. My repair should outlast the rest of the amp. I put about $15 worth of parts and a bit of labor into that amp head and the 4x12 cab that came with it (which also needed replacement jacks) and sold the head on CL for $50... So I ended up $35 ahead and with a free 4x12 cab loaded with Electro-Harmonix labeled Eminence drivers... Not bad for about an hours work.
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Pots too. There are amps that rely on the pots to ground various points in the circuit. The pots are not otherwise connected together. I add the necessary jumper wires to these amps. Otherwise you can't troubleshoot.