home studios equipment staff/friends booking/rates for sale forum contact

Garnet Pro sounds like shit - techs please help

All your geeky questions about electronics, microphones, tape machines, etc.

Moderators: kerble, Electrical-Staff

Garnet Pro sounds like shit - techs please help

Postby llllllllllllllllllllllll on Mon Oct 19, 2015 9:26 pm

OK - I've made videos as I've taken it to two different techs for a total of at least a couple hundred, and it's still not fixed. Basically, the clean sound (Stinger function off) starts to sound like crap after you've been playing it for a while. After you power it down and let it sit for about 15 minutes it sounds good again, but slowly starts to go bad.

The Stinger function *seems* like it's working fine, but but it's so loud and nuts sounding that it's hard to tell.

Note that on Garnet amps the noon position of the knob is '0.'

phpBB [media]


Where the Garnet starts to fuck up. This is generally after you've been playing it loudly for about 20 minutes or so.

phpBB [media]


The Stinger still sounds good!

phpBB [media]


The amp sounds great when you first turn it on.

Ideas? Any trouble shooting I can do on my own? I'm taking this back to the shop - if I can't fix it I'll at least try to get my money back.
llllllllllllllllllllllllllllllllll
User avatar
llllllllllllllllllllllll
Man with Encyclopedic Knowledge
Man with Encyclopedic Knowledge
 
Posts: 5117
Joined: Thu Jun 29, 2006 4:32 pm
Location: Texas

Re: Garnet Pro sounds like shit - techs please help

Postby biscuitdough on Tue Oct 20, 2015 11:19 am

If you let it sit on standby for 20 minutes without playing and then go for it, does it sound good or shitty? If good, does the shitty come on sooner than another 20 minutes in?

Usually this happens when a weak solder joint is being affected by the heat from the tubes, and the answer is to reflow every solder joint, a tedious process on older amps because you need to clean the board first, heat up and then suck away the solder, and then replace it with new (for best results, anyway). I suck at soldering so I take it to a tech, but my tech is diligent and passionate about his work, and not the usual sad old loadie you'll find at a guitar shop.
User avatar
biscuitdough
penguinologist
penguinologist
 
Posts: 1837
Joined: Tue Jun 17, 2014 12:28 pm

Re: Garnet Pro sounds like shit - techs please help

Postby llllllllllllllllllllllll on Tue Oct 20, 2015 11:53 am

biscuitdough wrote:If you let it sit on standby for 20 minutes without playing and then go for it, does it sound good or shitty? If good, does the shitty come on sooner than another 20 minutes in?


I'll check this and get back to you. I get the impression that this only happens after you're playing loud through the amp, as I've had techs assure me that they've left the amp running for a while, but I haven't left it on standby long enough to actually see for myself.

One thing I *know* the techs aren't doing is turning the damn thing up and hearing it for themselves! How does anyone get a hold of cool old amps and not wail on them for a while?
llllllllllllllllllllllllllllllllll
User avatar
llllllllllllllllllllllll
Man with Encyclopedic Knowledge
Man with Encyclopedic Knowledge
 
Posts: 5117
Joined: Thu Jun 29, 2006 4:32 pm
Location: Texas

Re: Garnet Pro sounds like shit - techs please help

Postby biscuitdough on Tue Oct 20, 2015 12:08 pm

It looks like these are of the Fender (or, "incorrect") style, in which the tubes dangle down from the chassis, letting all their heat rise into the most heat-sensitive components. Heat problems will be more common than with amps that use the Marshall (or "correct") configuration, in which the tubes thrust triumphantly upward from the chassis. After the issue is corrected, you might want to add a chassis fan.
User avatar
biscuitdough
penguinologist
penguinologist
 
Posts: 1837
Joined: Tue Jun 17, 2014 12:28 pm

Re: Garnet Pro sounds like shit - techs please help

Postby llllllllllllllllllllllll on Tue Oct 20, 2015 12:23 pm

But if the Stinger works fine all the time, then that should narrow things, right? I'm not very technical, but I'm guessing whatever is messing up is bypassed when the Stinger is on?
llllllllllllllllllllllllllllllllll
User avatar
llllllllllllllllllllllll
Man with Encyclopedic Knowledge
Man with Encyclopedic Knowledge
 
Posts: 5117
Joined: Thu Jun 29, 2006 4:32 pm
Location: Texas

Re: Garnet Pro sounds like shit - techs please help

Postby biscuitdough on Tue Oct 20, 2015 12:35 pm

llllllllllllllllllllllll wrote:But if the Stinger works fine all the time, then that should narrow things, right? I'm not very technical, but I'm guessing whatever is messing up is bypassed when the Stinger is on?


Possibly! But it doesn't get quieter when it starts to sound bad, does it? It just loses sustain and sounds well, shittier? It could be that the Stinger is enough of a boost to compensate. It really needs a tech to use a signal generator and inject a sine wave into the input and probe throughout the signal path to see where the signal starts degrading.

Reflowing the solder joints is the best shotgun approach here. If that fails, probing as described above (which is dangerous and requires specialized equipment) is the next step.
User avatar
biscuitdough
penguinologist
penguinologist
 
Posts: 1837
Joined: Tue Jun 17, 2014 12:28 pm

Re: Garnet Pro sounds like shit - techs please help

Postby llllllllllllllllllllllll on Tue Oct 20, 2015 3:28 pm

I see what you mean. I'm just going to do some research and see if I can find a great tech in Houston.

If I had any sense I would have just returned the damn thing when I first noticed the problem. Still a cool amp when it works, though.
llllllllllllllllllllllllllllllllll
User avatar
llllllllllllllllllllllll
Man with Encyclopedic Knowledge
Man with Encyclopedic Knowledge
 
Posts: 5117
Joined: Thu Jun 29, 2006 4:32 pm
Location: Texas

Re: Garnet Pro sounds like shit - techs please help

Postby biscuitdough on Tue Oct 20, 2015 4:20 pm

llllllllllllllllllllllll wrote:I see what you mean. I'm just going to do some research and see if I can find a great tech in Houston.

If I had any sense I would have just returned the damn thing when I first noticed the problem. Still a cool amp when it works, though.


How long have you had it back? Your existing techs might work with you if you explain that it takes 20 minutes of playing before the onset of trouble.
User avatar
biscuitdough
penguinologist
penguinologist
 
Posts: 1837
Joined: Tue Jun 17, 2014 12:28 pm

Re: Garnet Pro sounds like shit - techs please help

Postby llllllllllllllllllllllll on Tue Oct 20, 2015 4:30 pm

biscuitdough wrote:
llllllllllllllllllllllll wrote:I see what you mean. I'm just going to do some research and see if I can find a great tech in Houston.

If I had any sense I would have just returned the damn thing when I first noticed the problem. Still a cool amp when it works, though.


How long have you had it back? Your existing techs might work with you if you explain that it takes 20 minutes of playing before the onset of trouble.


Man, I have. I just got it back from the fourth trip to the tech. Took it to one guy twice before I tried to find someone else and another twice.
llllllllllllllllllllllllllllllllll
User avatar
llllllllllllllllllllllll
Man with Encyclopedic Knowledge
Man with Encyclopedic Knowledge
 
Posts: 5117
Joined: Thu Jun 29, 2006 4:32 pm
Location: Texas

Re: Garnet Pro sounds like shit - techs please help

Postby numberthirty on Wed Oct 21, 2015 1:30 am

llllllllllllllllllllllll wrote:But if the Stinger works fine all the time, then that should narrow things, right? I'm not very technical, but I'm guessing whatever is messing up is bypassed when the Stinger is on?


Any chance you have current "Gut Shots" we can see?
154 wrote:Are you in Voivod or something?
User avatar
numberthirty
King Shit of Fuck Mountain
 
Posts: 19392
Joined: Sat Dec 03, 2005 3:28 am

Re: Garnet Pro sounds like shit - techs please help

Postby biscuitdough on Wed Oct 21, 2015 8:20 am

Any chance you have the exact model and a list of what tubes are in it? Apparently they changed the design a lot through the years. Some models bypass the tone stack when the Stinger is on, some don't, and all perplexed the folks at the ax84 forum: http://www.ax84.com/bbs/dm.php?thread=286215
User avatar
biscuitdough
penguinologist
penguinologist
 
Posts: 1837
Joined: Tue Jun 17, 2014 12:28 pm

Re: Garnet Pro sounds like shit - techs please help

Postby TomWanderer on Wed Oct 21, 2015 10:46 am

I have no idea if this circuit is similar to yours, but my Sound City Concord had the same type of issue; sounded great for 15 or 20 minutes, then it would sound like garbage. It turned out there was a tiny, individual trim pot for each power tube that had been fried and was running fully open as a result. The power tubes would just get blasted. Sounding good at first, then would lose clean punch, then volume, eventually sounding weak and inarticulate.
TomWanderer
madame ooglepuss
madame ooglepuss
 
Posts: 256
Joined: Thu Apr 02, 2009 1:15 pm
Location: Milwaukee

Re: Garnet Pro sounds like shit - techs please help

Postby TylerSavage on Thu Oct 22, 2015 2:05 am

I see we jam at the same halls..

1. FIrst things first - swap all of the 12ax7s with ones from another amp and see if that fixes your issue. We know the power section is *probably* fine.

2. Otherwise like someone said, reflow the solder - Heat stuff is usually tube internal or solder joints being iffy. I swear I had this exact problem with my Pro, except it was all the time and I replaced the filter caps and all electrolytics and I was good.

If 1. or 2. don't work - check the electrolytics. do they look original? I think OG was mallory but don't quote me. You might have some electrolytics losing it when they're getting too hot .. sounds kind of like blocking distortion, although more constricted/farty. I have a sinking feeling this is what it is which sucks because its the most work/ordering effort.

Garnet schematics online are often mislabeled, and it's really hard to guage what schematic is for what amp. I have every garnet schematic on hand if you need it - What's the model designation on the plate on that back? I'm going to guess an L190, I cant see a clef.

I've got gut shots of mine but on my external drive at work, I'll try to remember to bring it home
User avatar
TylerSavage
matt damon
matt damon
 
Posts: 900
Joined: Tue Oct 29, 2013 7:37 am
Location: San Diego

Re: Garnet Pro sounds like shit - techs please help

Postby llllllllllllllllllllllll on Thu Oct 22, 2015 9:13 am

Guys thanks for all your help. I've had two rehearsals this week so I haven't been able to mess with the Garnet much, but I'll reply to this with answers and gutshots this weekend.

I'm pretty sure the caps have been replaced. One of the techs said there was nice stuff in there.
llllllllllllllllllllllllllllllllll
User avatar
llllllllllllllllllllllll
Man with Encyclopedic Knowledge
Man with Encyclopedic Knowledge
 
Posts: 5117
Joined: Thu Jun 29, 2006 4:32 pm
Location: Texas

Re: Garnet Pro sounds like shit - techs please help

Postby biscuitdough on Thu Oct 22, 2015 11:16 am

llllllllllllllllllllllll wrote:Guys thanks for all your help. I've had two rehearsals this week so I haven't been able to mess with the Garnet much, but I'll reply to this with answers and gutshots this weekend.

I'm pretty sure the caps have been replaced. One of the techs said there was nice stuff in there.


Some techs will (stupidly) replace the power supply filter electrolytics, but leave the bias supply and preamp cathode ones unchanged.
User avatar
biscuitdough
penguinologist
penguinologist
 
Posts: 1837
Joined: Tue Jun 17, 2014 12:28 pm

Re: Garnet Pro sounds like shit - techs please help

Postby whoisalhedges on Thu Oct 22, 2015 12:35 pm

TomWanderer wrote:I have no idea if this circuit is similar to yours, but my Sound City Concord had the same type of issue; sounded great for 15 or 20 minutes, then it would sound like garbage. It turned out there was a tiny, individual trim pot for each power tube that had been fried and was running fully open as a result. The power tubes would just get blasted. Sounding good at first, then would lose clean punch, then volume, eventually sounding weak and inarticulate.

I doubt it's a bias issue, because the Stinger circuit working SHOULD rule that out - I mean, the power tubes are still the power tubes, right?

How was yours fixed? I'm basically an idiot when it comes to matters electronical, but I enjoy the thory. Your profile says Milwaukee, I assume you took it to Blick? I don't know any shops in town but Rockhaus that do amp repairs in-shop, and even they send John the tough ones. Did he replace the bias trim pots or just throw in a resistor and make it fixed bias?

Honestly, I'd love to find out how cathode biasing would work in Sound City/Hiwatt amps - but that's getting WAY off tangent from the OP. ;)
"Country music must go on!" -- Austin J. Hall, September 11, 2001
User avatar
whoisalhedges
Eternal Bosom of Hot Love
Eternal Bosom of Hot Love
 
Posts: 3378
Joined: Mon Sep 26, 2011 2:27 pm
Location: Where they put chili on spaghetti, BBQ sauce on kielbasa, and men on the moon.

Re: Garnet Pro sounds like shit - techs please help

Postby llllllllllllllllllllllll on Thu Oct 22, 2015 1:20 pm

whoisalhedges wrote:I doubt it's a bias issue, because the Stinger circuit working SHOULD rule that out - I mean, the power tubes are still the power tubes, right?


Well, FM biscuitdough brought up a good point here - I remember I was in the middle of a band practice when my Bassman went down - luckily the Garnet had just arrived so I plugged it in. I couldn't figure out how to turn the Stinger off (I didn't have a footswitch, and the Stinger is automatically on, I think), so I pulled the 6WJ8 out and it worked fine for a while. When it started to do that crap plinky, staticy sound, I compensated with a Micro-Amp. It still had the problem, but I was able to compensate enough to get through practice. So, based on that, I believe the Stinger is probably hoss enough to cover up any electronic short comings that are happening.

Seriously, you could run a Fender Mustang through the built in fuzz and you'd go from banjo to Sleep at the flick of a switch.

Really wish this amp was working right now. My YBA-1 is great, but loses a lot of clank when you clean up w/ your guitar's volume knob.
llllllllllllllllllllllllllllllllll
User avatar
llllllllllllllllllllllll
Man with Encyclopedic Knowledge
Man with Encyclopedic Knowledge
 
Posts: 5117
Joined: Thu Jun 29, 2006 4:32 pm
Location: Texas

Re: Garnet Pro sounds like shit - techs please help

Postby biscuitdough on Thu Oct 22, 2015 2:02 pm

llllllllllllllllllllllll wrote:
whoisalhedges wrote:I doubt it's a bias issue, because the Stinger circuit working SHOULD rule that out - I mean, the power tubes are still the power tubes, right?


Well, FM biscuitdough brought up a good point here - I remember I was in the middle of a band practice when my Bassman went down - luckily the Garnet had just arrived so I plugged it in. I couldn't figure out how to turn the Stinger off (I didn't have a footswitch, and the Stinger is automatically on, I think), so I pulled the 6WJ8 out and it worked fine for a while. When it started to do that crap plinky, staticy sound, I compensated with a Micro-Amp. It still had the problem, but I was able to compensate enough to get through practice. So, based on that, I believe the Stinger is probably hoss enough to cover up any electronic short comings that are happening.

Seriously, you could run a Fender Mustang through the built in fuzz and you'd go from banjo to Sleep at the flick of a switch.

Really wish this amp was working right now. My YBA-1 is great, but loses a lot of clank when you clean up w/ your guitar's volume knob.


Try known working 12AX7s, as recommended here. This is the least likely, IMO, but it's also the easiest step to do at home.

On an amp this age, even if the cause of the immediate problem is not solved, you would not be wasting time/money by reflowing all the solder joints (especially grounds) and replacing any old electrolytic caps that weren't replaced before. Getting good clean solder connections for gigging reliability is best left to someone who solders often, so I'd take it to a tech or advanced hobbyist friend for this.

After that you end up having to look at dodgy old resistors that change their value wildly under heat conditions, etc. With a signal generator and probe, as I mentioned earlier.
User avatar
biscuitdough
penguinologist
penguinologist
 
Posts: 1837
Joined: Tue Jun 17, 2014 12:28 pm

Re: Garnet Pro sounds like shit - techs please help

Postby TomWanderer on Thu Oct 22, 2015 2:06 pm

whoisalhedges wrote:
TomWanderer wrote:I have no idea if this circuit is similar to yours, but my Sound City Concord had the same type of issue; sounded great for 15 or 20 minutes, then it would sound like garbage. It turned out there was a tiny, individual trim pot for each power tube that had been fried and was running fully open as a result. The power tubes would just get blasted. Sounding good at first, then would lose clean punch, then volume, eventually sounding weak and inarticulate.

I doubt it's a bias issue, because the Stinger circuit working SHOULD rule that out - I mean, the power tubes are still the power tubes, right?

How was yours fixed? I'm basically an idiot when it comes to matters electronical, but I enjoy the thory. Your profile says Milwaukee, I assume you took it to Blick? I don't know any shops in town but Rockhaus that do amp repairs in-shop, and even they send John the tough ones. Did he replace the bias trim pots or just throw in a resistor and make it fixed bias?

Honestly, I'd love to find out how cathode biasing would work in Sound City/Hiwatt amps - but that's getting WAY off tangent from the OP. ;)


Yes, Mr. Blick serviced the Sound City on more than one occasion. He has also repaired ALL of my other tube amps at one point or another over the last decade or so. I honestly don't know what I would do without him. He did replace the bias pots with sturdier components than came stock. Apparently the original bias pots were tiny plastic trim pots. The way he explained it to me, Sound City amps run the power tubes with an awfully high plate voltage to begin with, which can cause them to run through power tubes faster and be a touch unreliable in general. The sound when they're dialed in correctly can be totally worth the occasional headache, in my opinion.

The stock bias pots simply couldn't handle the load forever and crapped out after 35 or 40 years, supplying a fully open load the the power tubes. This made for the 15 min or so of fantastic sound as the tubes warmed up, then not so much as they kept going past the desired point.

Don't mean to derail the thread, I understand OP's troubles may not lie in the power amp section.
TomWanderer
madame ooglepuss
madame ooglepuss
 
Posts: 256
Joined: Thu Apr 02, 2009 1:15 pm
Location: Milwaukee

Re: Garnet Pro sounds like shit - techs please help

Postby TylerSavage on Thu Oct 22, 2015 9:20 pm

whoisalhedges wrote:
TomWanderer wrote:I have no idea if this circuit is similar to yours, but my Sound City Concord had the same type of issue; sounded great for 15 or 20 minutes, then it would sound like garbage. It turned out there was a tiny, individual trim pot for each power tube that had been fried and was running fully open as a result. The power tubes would just get blasted. Sounding good at first, then would lose clean punch, then volume, eventually sounding weak and inarticulate.

I doubt it's a bias issue, because the Stinger circuit working SHOULD rule that out - I mean, the power tubes are still the power tubes, right?

How was yours fixed? I'm basically an idiot when it comes to matters electronical, but I enjoy the thory. Your profile says Milwaukee, I assume you took it to Blick? I don't know any shops in town but Rockhaus that do amp repairs in-shop, and even they send John the tough ones. Did he replace the bias trim pots or just throw in a resistor and make it fixed bias?

Honestly, I'd love to find out how cathode biasing would work in Sound City/Hiwatt amps - but that's getting WAY off tangent from the OP. ;)



it could though be a bias issue on one of the 12ax7s though.. in that if one of the capacitors is shorting that's going to cause a mess, but you would probably see the tube red plating or it would die all together
User avatar
TylerSavage
matt damon
matt damon
 
Posts: 900
Joined: Tue Oct 29, 2013 7:37 am
Location: San Diego

Next

Return to Tech Room

Who is online

Users browsing this forum: andres.v, Bing [Bot], Facundo and 7 guests