Garnet Sessionman G250FTR Power Tubes Light Up

[tinkering]

This is my first repair topic on this forum. I started the thread decades ago but life derailed my focus. I guess my original thread is too old now so I will start anew.

We have a Garnet Sessionman that needs attention. I see a number of Garnet threads already started but I didn't see one on a Sessionman.

Symptoms:

- The Fuzz does not work. If you turn the fuzz pot up the power tubes light up like a Christmas tree, and it sounds like a train horn.
- There are some hums and buzzes that flipping the polarity switch does not eliminate.
- It was originally a 4x12" cabinet. It was a devil to move around so I separated the speakers at the hip. I removed the old Marsland speakers, halved the cabinet and put a couple of Yamaha speakers in. I made an extension cabinet out of the other half. I did a nice clean job of it all so please don't beat me. I am not sure if I ever wired the  speakers in properly so the impedance matched?
- I suppose the thing will need some new tubes, and capacitors and stuff?
- Fuse blows occasionally

I know some say Garnet doesn't rate with the big boys but others say it had a sound like no other... but I love it, and so does my son now.

I hope Hoffman has everything I need to revive this gem.
There may not be much in my original thread that isn't here but follow this link if you want to look: https://el34world.com/Forum/index.php?topic=20240.0

What should I do now, post a bunch of pics, and take the amp out of the cab?
Thanks

[tinkering]

Here is the schematic for the Garnet Sessionman g250ftr amp; the ftr = fuzz tremolo reverberation:

http://el34world.com/charts/Schematics/files/garnet/garnet_g250ftr_sessionman.pdf

[HotBluePlates]

... a Garnet Sessionman that needs attention. ...

These photos are as close as I've ever been to a Sessionman.  So these are just some ideas to get started:

- The Fuzz does not work. If you turn the fuzz pot up the power tubes light up like a Christmas tree, and it sounds like a train horn.

From the schematic (thanks for linking!) is looks like half the 6JW8 is used for the Fuzz circuit.  This circuit acts on the Ultra-Mix channel.  IF you pull the 6JW8 from its socket, do the power tubes stay happy?  No horn sounds?

- Fuse blows occasionally

How "occasionally"?  One an hour?  Once every 8 years?

If it tends to blow more often, try removing the power tubes from the amp, then turning the amp on.  See if the fuse holds.

[tinkering]

... a Garnet Sessionman that needs attention. ...

These photos are as close as I've ever been to a Sessionman.  So these are just some ideas to get started:

- The Fuzz does not work. If you turn the fuzz pot up the power tubes light up like a Christmas tree, and it sounds like a train horn.

From the schematic (thanks for linking!) is looks like half the 6JW8 is used for the Fuzz circuit.  This circuit acts on the Ultra-Mix channel.  IF you pull the 6JW8 from its socket, do the power tubes stay happy?  No horn sounds?

- Fuse blows occasionally

How "occasionally"?  One an hour?  Once every 8 years?

If it tends to blow more often, try removing the power tubes from the amp, then turning the amp on.  See if the fuse holds.

Those are great directions. I am super busy tommory but will get at it as soon as I can.
I will have answers for you.
Thanks

[tinkering]

... and I will post some pictures too.

[tinkering]

... a Garnet Sessionman that needs attention. ...

These photos are as close as I've ever been to a Sessionman.  So these are just some ideas to get started:

- The Fuzz does not work. If you turn the fuzz pot up the power tubes light up like a Christmas tree, and it sounds like a train horn.

From the schematic (thanks for linking!) is looks like half the 6JW8 is used for the Fuzz circuit.  This circuit acts on the Ultra-Mix channel.  IF you pull the 6JW8 from its socket, do the power tubes stay happy?  No horn sounds?

When the amp was warmed up I pulled the 6JW8 for a minute or two. The power tubes stayed happy. No christmas tree, no train horn

- Fuse blows occasionally

How "occasionally"?  One an hour?  Once every 8 years?

Once every 8 years probably.

If it tends to blow more often, try removing the power tubes from the amp, then turning the amp on.  See if the fuse holds.

I tried this anyway. When the amp was warmed up I shut it off. I pulled the power tubes out and turned it on. The fuse did not blow.
 
 With the power tubes reinstalled and amp warmed up I tried the fuzz on full. There was zero fuzzeffect, no christmas tree power tubes, and no train horn. I guess it is an intermittent problem. The worst kind!


EDIT: untangled quotes --HBP

[tinkering]

Trying to post some pics.
Having trouble.
Have to make files smaller. Later

[HotBluePlates]

The fear was "bum output tubes are blowing a fuse."  Since that doesn't seem to be the case, leave them installed for now.

From the schematic (thanks for linking!) it looks like half the 6JW8 is used for the Fuzz circuit.  This circuit acts on the Ultra-Mix channel.  IF you pull the 6JW8 from its socket, do the power tubes stay happy?  No horn sounds?

When the amp was warmed up I pulled the 6JW8 for a minute or two. The power tubes stayed happy. No christmas tree, no train horn

Okay, then the fuzz circuit or the 6JW8 is your problem.

   - Re-install the 6JW8 and see if the amp still malfunctions.  If yes, we'll troubleshoot further.

[tinkering]

All tubes in. Amp working well, except for the fuzz... as it has done for many years.

Have you ever heard a tube amp that didn't have any AC hum? This one has a bit but nothing too obtuse.

Thanks

[HotBluePlates]

All tubes in. Amp working well, except for the fuzz... as it has done for many years.

Need more detail on what that means.

Also, this thread centers on dealing with Garnet's Stinger fuzz circuit.

[tinkering]

All tubes in. Amp working well, except for the fuzz... as it has done for many years.

Need more detail on what that means.

Also, this thread centers on dealing with Garnet's Stinger fuzz circuit.

You said, "Okay, then the fuzz circuit or the 6JW8 is your problem.

   - Re-install the 6JW8 and see if the amp still malfunctions.  If yes, we'll troubleshoot further."

With the 6JW8 re-installed, the amp is working except for the Fuzz. That is the same as it was before I did the check by pulling the 6JW8, and the check by pulling the power tubes (to see if the fuse was going to blow). I hope I worded that right.

Does the G250FTR use the same Stinger Fuzz circuit as the Garnet LB190D Pro that you gave me the link to? I read that thread and was left behind a number of times as my knowledge is more limited than I would like to admit.

When I pulled the 6JW8 I noticed the pins were quite a dark overheated color. Could it be as simple as a faulty tube? Where the heck can I find a tube tester in Calgary?

Where should I start?

[HotBluePlates]

With the 6JW8 re-installed, the amp is working except for the Fuzz.

I don't know what "not working" means.
  - Amp doesn't make sound?
  - Amp makes sound, but it's not fuzzy/distorted?
  - Amp makes fuzzy/distorted sound, but it's too quiet?
  - Amp makes fuzzy/distorted sound, but it's full-loudness only?
  - Fuzz doesn't change bright/dark tonality when turning the tone control?

  - Other??

When I pulled the 6JW8 I noticed the pins were quite a dark overheated color. ...

The color is harmless; most old tubes have darker pins.

Truly overheating the tube would melt the plate structure and/or glass.

Does the G250FTR use the same Stinger Fuzz circuit as the Garnet LB190D Pro that you gave me the link to?

It's "the same, but different."  Like a Mustang and a Maxima have different details but the same broad characteristics.

[tinkering]

With the 6JW8 re-installed, the amp is working except for the Fuzz.

I don't know what "not working" means.
  - Amp doesn't make sound?
  - Amp makes sound, but it's not fuzzy/distorted?
  - Amp makes fuzzy/distorted sound, but it's too quiet?
  - Amp makes fuzzy/distorted sound, but it's full-loudness only?
  - Fuzz doesn't change bright/dark tonality when turning the tone control?

  - Other??
I'm sorry, I should have known you wanted the characteristics of the fault.

The Amp makes good sound, but it's not fuzzy/distorted at all.

Sometimes the power tubes would glow like lightbulbs, and the amp sounded like a train horn when I would turn the Fuzz pot on (it doesn't seem to be doing that currently).

When I pulled the 6JW8 I noticed the pins were quite a dark overheated color. ...

The color is harmless; most old tubes have darker pins.

Truly overheating the tube would melt the plate structure and/or glass.

Does the G250FTR use the same Stinger Fuzz circuit as the Garnet LB190D Pro that you gave me the link to?

It's "the same, but different."  Like a Mustang and a Maxima have different details but the same broad characteristics.

[tinkering]

"It's "the same, but different."  Like a Mustang and a Maxima have different details but the same broad characteristics."

I get it. Slightly different configurations, component values etc. but basically the same concept. Thanks

[HotBluePlates]

The Amp makes good sound, but it's not fuzzy/distorted at all.

Do you have the footswitch?

The schematic is unclear on this point, but appears to have the footswitch make the connection between the pentode section cathode components (6JW8 Pin 7) and ground.  If this were true, the Fuzz wouldn't work at all unless the footswitch is plugged in (seems like an odd choice, but Fender did the same with tremolo in bigger amps).

This is how the (6JW8 version) LB190D works, though it also has a panel-mounted switch to do the same thing (indicated as an "X" inside a circle).

[tinkering]

Ahha! Very interesting! I am not sure if I ever tried a foot switch for the fuzz.
I will check that out tomorrow. I used to have an old 2 switch foot switch. Excellent!

[WimWalther]

The schematic is unclear on this point, but appears to have the footswitch make the connection between the pentode section cathode components

Unclear, or clearly in error?

Because as drawn, the FS would have no effect. Unless my eyes deceive me, it redundantly connects a grounded line to ground.. again.

I suggest that the OP trace out the circuit as it's actually built, to see what the schematic may have gotten wrong.

[tinkering]

The schematic is unclear on this point, but appears to have the footswitch make the connection between the pentode section cathode components

Unclear, or clearly in error?

Because as drawn, the FS would have no effect. Unless my eyes deceive me, it redundantly connects a grounded line to ground.. again.

I suggest that the OP trace out the circuit as it's actually built, to see what the schematic may have gotten wrong.

I see what you mean with the schematic. The part of the Wide Range channel using the 6JW8 and 12AU7 is shown to be grounded; ok, but is that whole section dependant on the Ft Sw to be grounded? Did I word that correctly?
Over on the right side of the Wide Range that is using 1/2- 6JW8 there seems to me to be a missing line or two. The TR Ft Sw is switched to ground. The Rev Ft Sw seems to be hanging in mid air; I assume those long vertical rectangles are symbols for a switch?
I think you are right, Iam going to have to check the physical circuit against the schematic. Thanks!

HotBluePlates, what do you think of all this?

[PRR]

> what do you think of all this?

I think what Wim already said:

> ..trace out the circuit as it's actually built, to see what the schematic may have gotten wrong.

Garnet's schematics were causal notes to remind him what he did, not full-fledged Documentation.

[tinkering]

> what do you think of all this?

I think what Wim already said:

> ..trace out the circuit as it's actually built, to see what the schematic may have gotten wrong. Ahh, ok, right on! I'll pull the chassis and trace it all out.

Garnet's schematics were causal notes to remind him what he did, not full-fledged Documentation. .
Excellent, that is excellent to know. Thanks

PRR, You are familiar with Garnets? Have you worked on them before? THANKS

[tinkering]

 
That is the best I can do for a picture. Pretty crappy.

Moreover though, the main problem with the fuzz is that it only works with the footswitch, just like HotBluePlates said. How can I feel dumber than usual? SO THE FUZZ WORKS BUT ONLY BY THE FOOT SWITCH.
The Fuzz works only on the Ultra Mix channel (also like HBPs figured) but the Tremolo and Reverb work on both Ultra Mix and Wide Range channels.

I have two 8 ohm speakers in parallel, so that matches the amp's 4 ohm impedance.
What config would I use if we want to plug that old 1/2 cab 2x12 into the EXT output? Is the EXT output jack 4 ohms impedance as well?... or do the combined 4 x 12s need to be 4 ohms (and not use the EXT output at all)? Again, I hope I'm wording that right?

[sluckey]

I find it very hard to follow this thread.
Especially when the font colors keep changing.
Would probably be easier to follow if you would use the quotes correctly.

[tinkering]

I find it very hard to follow this thread.
Especially when the font colors keep changing.
Would probably be easier to follow if you would use the quotes correctly.

Hi sluckey,
Long time no hear. It's been 25 years or something since I posted my original topic. I think that might be a record, 25 years to find the solution, and then it turns out that the idiot (me) was using the amp incorrectly. As for the misuse of the 'quotes' function, those multiple long quotes make it hard to track my replies because my black text gets lost in the yards of everyone elses black text. Not only do I feel like a freakin idiot, now I feel like a scolded idiot. That's ok, I can handle it. I've had lots of practice 
I am done with the colored ink.
How are you doing? I like this forum. It's neat that you are still here 25 years later.

[tinkering]

Can someone help me with the speaker configuration post (sluckey, it's the blue one 😃)?
You'll be confused too after you read my prose😳
Thanks to all you folks.

[PRR]

....my black text gets lost in the yards of everyone elses black text. ...

It is not necessary to quote-back ALL of the post you are replying to. While wantonly chopping another person's writing can be rude, if it is properly quoted with link, we can always go back and see what he really said in context.

40 years ago a sysop told me "one line". That was also 1200 baud and $25/hr, things are different, but he was right. The brain can't process massive quotebacks.

[WimWalther]

Can someone help me with the speaker configuration post (sluckey, it's the blue one 😃)?
You'll be confused too after you read my prose😳
Thanks to all you folks.

This depends on how your EXT jack is wired - that is, whether or not it disconnects the internal speakers when you jack-in.

As to the impedance of the EXT jack, if it's not printed on the chassis then you'll have to consult the documentation.

But if the EXT jack is wired to connect the external speakers in parallel with the internals, that's two parallel 4R loads, or 2R total.. and definitely not a recommended setup.

(It could be played safely at lower volumes, but that defeats the whole point of adding another speaker set - right? )

[tinkering]

I hear you PRR.
I usually do a better job of all that. More cut and paste, and less clicking the quote button it is. I don't want AI to calculate my algorithms and class me as an idiot🌞
Thanks for all your help.

[tinkering]

@WimWalther:
-When I jack-in to the EXT speaker jack, the internal SPEAKER jack in unaffected.

There doesn't seem to be any output from the EXT speaker jack.

-A SINGLE label indicating 4 ohms impedance is shared by both the INTERNAL speaker output jack and the EXT speaker output jack...

-The original cab was 4-12s. I cut it down to 2-12s. I forget the config for 4 speakers. How would I wire 4-12s to get 4 ohms R? I'm assuming the original Marsland speakers were 8R each.

[WimWalther]

Not sure why there's no output from Ext. You'll have to check the docs or look inside.

There's no way to wire 4x 8R drivers to get 4R. Your options are 32R, 8R or 2R.

ETA: For 4R, you'd need 4x 16R or 4R drivers.

[sluckey]

Hi sluckey,
Long time no hear. It's been 25 years or something since I posted my original topic...

...It's neat that you are still here 25 years later.

Finally, something I understand.   
You joined and made your first post in April 2016, almost 8 years ago. And I've only been here since 2006, almost 18 years.

[tinkering]

Not sure why there's no output from Ext. You'll have to check the docs or look inside.

There's no way to wire 4x 8R drivers to get 4R. Your options are 32R, 8R or 2R.

ETA: For 4R, you'd need 4x 16R or 4R drivers.

I wonder what Garnet used 16R or 4R? I know they were Marsland but they weren't the best of speakers. They had a desirable sound but they didn't hold up, I think I heard.
I have one of the originals here but there are no markings on it.

I'll check that EXT jack wiring one day.
I can't seem to find any signs of those speaker jacks on the documents. There might be something on the 3rd or 4th page but I'm not the best at reading schematics. On the upper right side it mentions 4R or 8R tap, 'on some models'? What is that about?

[tinkering]

@sluckey:
I must have been on a different forum 25 years ago. Life de-rails
a guy on some things! I remember now, I was on a fire tower when I started this topic 8 years ago. I'm glad you guys are still around.
I still don't know why occasionally those power tubes light up and I get the train horn. I'll probably be on here to sort that out.
Thanks
tinkering