Pignose G40V Project

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Littlewyan
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Pignose G40V Project

Post by Littlewyan »

I bought myself a project!

Its a Pignose G40V Amp that doesn't work. The shop I bought it from received it to see if they could repair it cheaply, but they determined that the PT had blown as it was drawing current without anything on the secondaries, so the customer didn't want it.

On first inspection I can see that someone has put a 4A fuse in the 1A fuse socket........There is also a fuse socket inside the amp that requires a 5A fuse which is missing. On closer inspection I can see that all of the filter caps need replacing as they are bulging. This linked with the 4A fuse is probably why the PT blew.

Plan of action:
1. Replace PT with one that has a slightly lower HT. Ampmaker has one that should be perfect, giving me a HT of 360V or 250V if I wish.

2. Rewire the fuse sockets so they are on the live wire and not the neutral!!!!

3. Replace Filter Capacitors.

If anybody looks at the schematic for this amp they will see it looks very much like an amp from the 80s made by a company called Marshall :D.

Also I noticed that the HT secondaries had been disconnected (for testing the PT) but the Heater Secondaries hadn't. Maybe with any luck they forgot to remove the valves when testing. Doubtful but you never know. I'm hoping to do some testing this week. I'll upload photos later.
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M Fowler
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Re: Pignose G40V Project

Post by M Fowler »

Good little amp here is a mod page.
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Littlewyan
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Re: Pignose G40V Project

Post by Littlewyan »

Ah yes I had a little read through that. Its a good guide :). I don't think I'll do the tonal mods as I have my own ideas for that, but the bias pot is a good idea and I may utilize the internal fuse holder for the HT.

If I swap the PT I will have two secondaries on the new PT. So I may do a voltage switch to go from 360V to 250V, which I believe should be roughly either 20W or 10W with 6V6s.

I will also probably mod the pre amp to be like the Slash JCM800, but we'll see. I just want to get it running first so I can see what it sounds like stock :).
bluesfendermanblues
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Re: Pignose G40V Project

Post by bluesfendermanblues »

In case you want to update the cabinet, here's a great idea :-)

http://photobucket.com/images/pignose%2 ... conversion
Diva or not? - Respect for Mr. D's work....)
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Littlewyan
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Re: Pignose G40V Project

Post by Littlewyan »

That does look pretty awesome. Its staying a combo for now though :D. Might upgrade the speaker at some point.
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M Fowler
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Re: Pignose G40V Project

Post by M Fowler »

I like Steve Aloha's Hot Rod Tweed based off the Pignose GV40. Hot little amp and the guy that bought it from me is gigging it like mad.

Mark
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Stevem
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Post by Stevem »

I have had one since they first came out in 01 , and for the 200 Dollar price you can't say a bad word about!

I put in Steve's mods some years ago and also install fast recovery diodes, a OT center tap fuse and a better quality input jack.

Note that even with really strong output tubes on 125 volts of wall out let voltage the amp will only do 33 watts of RMS power which is good as even if it could do 36 watts that stock OT is small on mass!

A small fan is needed in the rear of these to keep those stock transformer's comfy!

These sound wonderful thru a 4-12 cab, yes very Marshall like!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!😊

Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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Littlewyan
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Re: Pignose G40V Project

Post by Littlewyan »

I have finally tested this amp and can confirm that the PT is shorted. Put my current limiter on it with a 100W bulb and it lights up very bright as soon as I turn it on. Currently trying to find a replacement PT.
Stevem
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Post by Stevem »

If fixed one with a dead PT 6 years ago for a guy and mounted the PT on the floor of the amps cabinet so I could put one in of the mass / core size needed!

It's a bit more work to extend the wires , but well worth it being as its your amp.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!😊

Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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Littlewyan
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Re: Pignose G40V Project

Post by Littlewyan »

Probably the best place for it given the lack of space inside. I'm trying to lower the wattage though to save on heat. My 35W and 50W amps are already too loud so I wanted this one to run between 10W and 20W.

I was thinking of going for a PT with a lower HT. One PT I'm looking at has two windings so I can have either 250VDC or 360VDC. Should be good with 6V6s. Should run cooler too. May swap the OT out as well as that will probably be too low impedance for 6V6s. I'm guessing the current unit is around 4.2K.

Need to take some measurements later to see if this new PT will fit.
Gibsonman63
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Re: Pignose G40V Project

Post by Gibsonman63 »

Interesting. The article from Mr. Fowler cites Dennis Kager as the designer, if I read it correctly. Same guy behind Sundown Amps. Sorry to derail.
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Littlewyan
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Re: Pignose G40V Project

Post by Littlewyan »

He also worked at Ampeg before Sundown I think
pdf64
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Re: M

Post by pdf64 »

Stevem wrote:I put in ... a OT center tap fuse ...
Did you check the screen grid current draw with the plates de-energised, ie to simulate a blown CT fuse?
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Littlewyan
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Re: Pignose G40V Project

Post by Littlewyan »

I think I've found the right transformers for the job.

http://www.tube-town.net/ttstore/Transf ... ::527.html

120mA should be enough HT current I believe for the 6V6s as I'm going to use an OT with an 8K primary.

For the OT I have two choices

http://www.tube-town.net/ttstore/Transf ... :5889.html

http://www.tube-town.net/ttstore/Transf ... :3971.html

Leaning more towards the 18W OT as it has a bit more iron than the 15W so should have nicer bottom end.
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Littlewyan
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Re: Pignose G40V Project

Post by Littlewyan »

Parts ordered. I went for the 18W OT.

I know I promised photos, I will upload some soon. Been rather busy! I think the mods I will carry out first are, install new PT and OT, install new filter caps, make bias adjustable, redo some of the wiring around the sockets and then I want to see how it sounds.

I already have some other circuit tweaks I'm going to make, but am interested to see how it sounds first. I bet judging by the wiring that this amp will squeal and hum with everything turned up.
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