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Discussion Starter #1
I got this Garnet 200 this week and a previous mod repair was done on it.

From what I could figure , this rig was a rental and all the work done was from the shop itself...

I know that a pot is missing for the stinger, it was broken off and the circuit is entirely there. The amp works flawlessly just no stinger at the moment.

Now for the repair... This transformer was added ontop of the chassis which is not stock.

At first, I thought it was a replacement choke but the original choke is still inside and connected...
 

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Discussion Starter #2 (Edited)
The new transformer gets its power directly from the AC line and goes to a new added circuit . New transformer to circuit ( circuit is one cap and 2 diodes) , bleu and white wire.

This new circuit( circuit is one cap and 2 diodes) goes directly to tube 1 only on pin 5 and 6. These are the 2 green wires...

Anyone know what this might be ??? :confused:

Help !!! MJF$#
 

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You're in luck! I have that exact same amp, but with different knobs on it. And it's totally virgin, never been touched. I'll take some pictures of the internals when I get home tonight.
The stinger needs a foot switch to operate (or short out the footswitch jack). You have some strange & unusual things going on in there for sure. I see several "wtf's".
That extra transformer with the blue & white twisted wires.......diodes, caps, and the light green twisted pair.......they don't belong. I'd almost swear mine doesn't have any orange drops either.
 

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What tube(s) and pin(s) thereof is that transformer connected to?

My first thought is that the original PT had the 6.3V (or 5V if tube rectified) secondary developed an issue (short or open) and they replaced it with this small tx because it's cheaper than replacing the entire PT (like a lot cheaper), the rest of which still works.

You can confirm this by providing the info above but also :

- checking if there are any unused leads on the original PT (i.e. that were replaced by this new Tx)
- checking that there is nothing else connected to this PT other than the tube heaters

The orange drops don't necessarily have anything to do with a mod; in an amp this old you'd expect some caps to have been changed out.
 

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I can't tell exactly where the green wires go from that add on rectifier, but the resistor values look similar to what Garnet puts around the bias to output tubes. Also the way the diodes are wired off the transformer will give you a negative voltage. It's a full wave negative supply by the looks of it. Probably to replace the bias supply for some unknown reason.
The workmanship is very suspect as well.
I'd get this to a reliable shop ASAP.
 

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Discussion Starter #7 (Edited)
What tube(s) and pin(s) thereof is that transformer connected to?
the 2 green wires are connected to pin 5 and 6 of the first power tube...

Nothing else is connected to this transformer.
No other wires is disconnected !


Since this seems to be a small power transformer and a cap and diodes were added before the tube . was thinking maybe the amp had a problem with rectifier circuit on one channel and this was his quick fix ??? :eek:
 

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Discussion Starter #8
The workmanship is very suspect as well.
I'd get this to a reliable shop ASAP.

Would your first guess be a problem with the rectifier circuit ?

I was thinking of changing the cap and diodes in the rectifier and wire it back to stock first...
 

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Would your first guess be a problem with the rectifier circuit ?

I was thinking of changing the cap and diodes in the rectifier and wire it back to stock first...
No - the rectifier is feeding the plates just fine (and that's a higher voltage)

the 2 green wires are connected to pin 5 and 6 of the power tubes...

Nothing else is connected to this transformer.
No other wires is disconnected !


Since this seems to be a small power transformer and a cap and diodes were added before the tube . was thinking maybe the amp had a problem with rectifier circuit on one channel and this was his quick fix ??? :eek:
5 is grid (so @dtsaudio is on to something re the bias voltage) and 6 is not used (so they probably used it as an anchor point for some of the added components):



The question is why they'd put in a separate Bias power supply vs using (modifying as necessary ) the original one? ... Looking at the schem for the B190D (which I assume this is), the bias supply comes off the PT primary so it is not isolated (it goes through a choke just before hitting the tubes, labelled T3 vs CH. as the choke in the power section, but the secondary is not connected or even pictured). Maybe someone didn't like this and decided isolation was required. That could even be the original T3 in there, repurposed. Later ones do away with T3 and tap the bias supply off the PT secondary, so are isolated.
 
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Discussion Starter #10
The question is why they'd put in a separate Bias power supply vs using (modifying as necessary )?

They didn't know how to bias ? :confused:

All tubes are original Garnet tubes... its not like a tube blew or anything.... nothing apart from the power cord was changed inside... erverything is original exept this added transformer connected to the tube socket !!!:confused:
 

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Discussion Starter #14

Big thanks Lincoln!

Yours looks super clean compared to mine...

My mess is that badly installed power cord and the added transformer which I have no clue as to why its there...

I have to work outside of town for 2 weeks and will tackle this as soon as I get back... first by changing the power cord and wiring it up to the fuse and remove the death cap and then by disconnecting this transformer... see if it will work just as good as it is right now !

This thing is clean... not a hiss when on ! :confused:
 

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Discussion Starter #16
Apart from me having an extra orange drop on my second tube and that transformer, they are identical...

Thanks Lincoln for taking the time to take a picture ! Easier to check with a picture...
 

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Does appear to be an "upgrade" to the bias circuit although hard to see all of the connections. Maybe an attempt to get a higher (more negative) bias voltage. Definitely would be putting it back to stock if it was mine.
 

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It's definitely an attempt to modify the bias circuit. The question is why. Did the modder not know what he was doing, is it supposed to be an upgrade or has something else failed and the incompetent boob who fixed it didn't know any better.
What needs to be done is a step by step through the amp wiring. Are the original bias parts still there, are they damaged? All voltage need to be checked to see they fall in line with what should be there. Then I would put things right. I said this earlier, the work is crap, and this amp deserves to be done right.
 
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