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Discussion Starter #1 (Edited)
I've been working away on a 6G16 brownface Vibroverb clone build. A very busy board in some places, but I went slowly & carefully and I think it's all right.
Vibroverb1.jpg
One thing that threw me for a loop though is the treble pots the build asks for. 350K with a 70K tap. Huh???
Wtf? Of course you never notice that sort of thing until you're well into the build.......and none of your regular suppliers sells anything like that. I'm still looking for some. Guess I'll switch and work on the other side of the amp for a while. :rolleyes:
 

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Good luck with that build Dave. I', still going to insist on you building me one at some point. Or helping me put something together. I will not relent! Those Amps in your music room look and sound fantastic.
 

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Discussion Starter #10 (Edited)
I've been working away at this build between glue-ups on a guitar repair. Put the transformers in, and I'm in the process of hooking up the PT and cap board wiring.
Vibroverb3.jpg

I can see a fire up in the not too distant future. Hopefully one without fire or smoke :)

I'm torn between hooking up the standby switch or not. The schematic has full B+ voltage interrupted by the standby switch. I know the heaters will be on and the tubes will be ready, but won't that still be a shock to filter caps and the tubes? I'm thinking that the GZ34 will provide all the protection I need.

Anybody know what to do with the orange wire on this Hammond 290CX power transformer? it shows between the primary and secondary windings. I'm not familiar with its function.
https://www.hammfg.com/files/parts/pdf/290CX.pdf
 

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I'm torn between hooking up the standby switch or not. The schematic has full B+ voltage interrupted by the standby switch. I know the heaters will be on and the tubes will be ready, but won't that still be a shock to filter caps and the tubes? I'm thinking that the GZ34 will provide all the protection I need.
Agree that GZ34 is all the protection you need. If you can live without the standby's 'mute' function, I'd leave it out.
 

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Discussion Starter #14
Vibroverb4.jpg
Here's the flip side. Wiring is all done now except the tube heater wiring. I always do it last so I can avoid all the other wires and things when running the heater wires.
 

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Discussion Starter #15 (Edited)
And it's cabinet time! I use a jig on my table saw called an Incra I-Box for cutting the box joints for the corners
Vibroverb5.jpg

Like magic, you have a box. All you need is glue and some clamps. In case you're looking at this going "wtf", I always leave the top of the box run wild for width. It gets trimmed when I cut that top angle you see on all the Fender cabinets.
Vibroverb6.jpg
 

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That brings back memories, most of them bad. I had a jig I attached to my bench and used a router to make the notches. It was a lot of work, especially for all the firewood byproduct. I surely would have used this if I'd known about it. Nice work!
 

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Discussion Starter #17
Can anyone tell me, WHY on ever amp I build, I get feed back and I have to switch the blue & the brown wires from the power tubes to the output transformer? Every one. I position those wires according to the layout diagram. Is there a secret? Or is just truly hit & miss and I'm consistently missing?

Anyway........the fire up went well. I had to re-solder one heater wire on a 12Ax7. I found that while checking voltages before I put tubes in it. I'll swap those OT wires over and plug a guitar into it.
I broke a GZ34 while putting it in. The glass just broke when I pushed on it. Must have been damaged or something.
 

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Discussion Starter #19
Murphy's Law!
Dam that Murphy guy! He's really starting to chaff my bag.

The tremolo on a 6G16 is awesome! The adjustable bias I put in is working perfectly. I've got some trouble shooting to do on the reverb however. It's not working. :(
 

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Can anyone tell me, WHY on ever amp I build, I get feed back and I have to switch the blue & the brown wires from the power tubes to the output transformer? Every one. I position those wires according to the layout diagram. Is there a secret? Or is just truly hit & miss and I'm consistently missing?
No, I can't tell you but it won't stop me from trying. ;)
There are 3 places phasing can get flipped. Are these various models or same layout? Single ended are more prone to be miswired as far as colour code goes, but you said blue and brown wires, so I take it you mean push-pull.
The 3 places I referred to are OT primary, OT secondary, and PI plate/power tube grid connections.
1)If the OT secondary wires are reversed, you will end up out of phase. This is most likely when there are only 2 wires at the OT secondary (single impedance type). In this particular amp, and many other Fenders of similar vintage, make sure black is ground, not green. (an easy mistake to make as both colours can be used to denote 'ground')
2)If the OT primary wires are reversed, again you will be out of phase. This is the most common error when an OT is replaced.
3)If the wires are reversed at the power tube grids (or PI plates) you will end up out of phase. This is probably the most likely suspect. Sometimes the schematic/layout is in error as far as the PI pin numbers.

All that being said, it's better to always check that the phasing is correct anyway. Sometimes you don't get the obvious squeal and just get weird problematic oscillations. For any amp that uses NFB, lift the nfb resistor and verify that gain is slightly reduced when NFB resistor is connected.
 
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