TalismanRich Posted April 20, 2014 Share Posted April 20, 2014 I had the 525 out, was grooving along with the Patriot. Nothing special, a little Hendrix with the TS-9 and the Deja Minivibe for the effects. Volume was only about 1/8, not even to a quarter. Suddenly it barks out this horrid buzzing. It sounded like the plug had been pulled out and the tip was hitting without a ground. That couldn't be the case because I was using my GT cable with a silent tip and the plug was still in! So I immediately it the standby, then the power switch. I unplugged the guitar and hit the power switch. BUUUUUUZZZZZ! Now comes the debugging process. I'm thinking the first thing would be to pull the first 12AX7s to see if its post preamp, perhaps in the reverb section or phase inverter section. The preamp tubes are EH and JJ. The PI is an EH. 6L6s are Sovtek, and the Rectifier is a JJ. I've got spare power tubes and preamp tubes. I might pick up another GZ34 just in case. Any words of wisdom before I swap out all the tubes? I thought about pulling the chassis to check for obvious blown caps or resistors. I haven't done that. Anyone had that same symptom before? Hopefully, I'll get this thing sorted out and cranking before PSP, otherwise I'll have throw the DSL401 in the car. Link to comment Share on other sites More sharing options...
Billgelder Posted April 20, 2014 Share Posted April 20, 2014 Sounds like a grounding issue. I would pull the chassis and do a full visual inspection. Then PM Mike. Don't you just love those GT cables they are all I use. Link to comment Share on other sites More sharing options...
golferwave Posted April 20, 2014 Share Posted April 20, 2014 Calling Slider313 ... the amp whisperers expertise is needed. Link to comment Share on other sites More sharing options...
schundog Posted April 20, 2014 Share Posted April 20, 2014 Good luck with the fix, Rich.... However, it wouldn't be the end of the world if you brought that Marshall; I used it a couple of years ago at PSP, and it sounded pretty darn sweet! Link to comment Share on other sites More sharing options...
LK155 Posted April 20, 2014 Share Posted April 20, 2014 Rich, Being at best an amateur tinkerer, I suggest if you're changing tubes you do them one at a time to determine which one's the culprit. If swapping them all out at once solves the problem, you won't know which one is the cause. Good luck. Link to comment Share on other sites More sharing options...
Spectrum13 Posted April 20, 2014 Share Posted April 20, 2014 Check the JJ GZ34 they had a bad run a few years back. Try a TAD STR Link to comment Share on other sites More sharing options...
Kuz Posted April 20, 2014 Share Posted April 20, 2014 Recifiers generally work, or they just quit. Sounds to me like a microphonic preamp tube or internal grounding issue. DOES the buzz occur with the input cord NOT in the amp? if so the input jack clip might need replaced. Have you tapped the preamp tubes with a plastic spoon or chop stick? Here is what I would do: 1) Change only the power tubes first 2) If the power tubes aren't the problem, next try the Phase Inverter (last preamp tube closest to the power tubes). 3) If the PI & Power Tubes aren't the issue, try changing one at a time, the preamp tubes starting with V1 (the opposite side of the PI tube) Probably the BEST thing to do, before any of the above, would be to PM Slider313 (Mike)!!!! Link to comment Share on other sites More sharing options...
Gitfiddler Posted April 20, 2014 Share Posted April 20, 2014 Patriots are so well built, that most any quality amp tech can diagnose and repair them. But as stated, start with the easy stuff...tubes. The innards of that amp are a clean, hand-wired, point-to-point thing of beauty. Link to comment Share on other sites More sharing options...
slider313 Posted April 20, 2014 Share Posted April 20, 2014 It sounds like a sprung input or one of the wires to the input not making contact. I highly doubt it's tube related. Link to comment Share on other sites More sharing options...
CJTopes Posted April 21, 2014 Share Posted April 21, 2014 Just had the same thing happen in one of my Riveras. Was a bad power tube.... Link to comment Share on other sites More sharing options...
TalismanRich Posted April 22, 2014 Author Share Posted April 22, 2014 Its probably going to be Saturday before I dive into this thing. I've got a pair of EL34s sitting on the shelf, so I might just put a new GZ34 on order and then install that with the EL34s to see how those sound. Link to comment Share on other sites More sharing options...
TalismanRich Posted April 27, 2014 Author Share Posted April 27, 2014 I pulled the preamp tubes and the PI. Fired it up and it was the same. I pulled a pair of JJ 6L6s off the shelf and put them in and when I fired it up it was better, but there is still some noise. I'm thinking the 5AR4 has gone taking the 6L6s out, so I've got another rectifier tube on the way. Tonight, I'm pulling the chassis just to check solder joints, caps and resistors. I also found that one of the 6V6GTs in my National is where my noise is coming form. VERY microphonic. It sounds like springs bouncing around. Its an RCA NOS tube. I have a pair of TAD 6v6GTBs on the way as well, just to try them out. They should be here by the end of the week. Hopefully, I'll have things cranking again by next weekend. Link to comment Share on other sites More sharing options...
slider313 Posted April 27, 2014 Share Posted April 27, 2014 I pulled the preamp tubes and the PI. Fired it up and it was the same. I pulled a pair of JJ 6L6s off the shelf and put them in and when I fired it up it was better, but there is still some noise. I'm thinking the 5AR4 has gone taking the 6L6s out, so I've got another rectifier tube on the way. Tonight, I'm pulling the chassis just to check solder joints, caps and resistors. The 5AR4 would not "take out" your 6L6's. Rectifier tubes either work or fail. Two symptoms of a bad rectifier would be, blowing your fuse or no sound at all. A rectifier can produce some noise but it's usually a slight "rattle" or "sizzle" on certain notes. What would stress your 6L6's is a bad screen resistor, your tubes are biased too hot or there's a large mis-match between tubes. A mis-match would produce hum and, if large enough, would have one tube running much hotter than the other and causing premature wear. Link to comment Share on other sites More sharing options...
Spectrum13 Posted April 27, 2014 Share Posted April 27, 2014 The 5AR4 would not "take out" your 6L6's. Rectifier tubes either work or fail. Two symptoms of a bad rectifier would be, blowing your fuse or no sound at all. A rectifier can produce some noise but it's usually a slight "rattle" or "sizzle" on certain notes. What would stress your 6L6's is a bad screen resistor, your tubes are biased too hot or there's a large mis-match between tubes. A mis-match would produce hum and, if large enough, would have one tube running much hotter than the other and causing premature wear. Slider, I can't do much more with an amp than clean contact points, change out speakers and tubes BUT I did have a bad JJ 5AR4 rectifer in my Swart. The amp worked but hummed real loud, was metalic and would shock me. However, having spare tubes around is not a bad thing. Link to comment Share on other sites More sharing options...
TalismanRich Posted May 10, 2014 Author Share Posted May 10, 2014 After changing out every tube in the Patriot and having no change, it went into the shop yesterday. They're a bit behind, so it will be a couple of weeks. I couldn't find any problems with parts or solder joints. The screen grid resistors were spot on. I think they read 987 for 1K resistors. No obvious bulging caps, or fried resistors anywhere. While I had it open, I snapped a few pics. Its typical Heritage amp work... neat and tidy. Link to comment Share on other sites More sharing options...
TalismanRich Posted May 10, 2014 Author Share Posted May 10, 2014 On another note, I put the TAD 6v6GT tubes in the National Supreme, and magically the noises were gone. One of the old 6V6s was extremely microphonic. The amp still has the strong midrange and goes into that nice overdrive with ease. For now, its healthy and ready to rock. Link to comment Share on other sites More sharing options...
Gitfiddler Posted May 10, 2014 Share Posted May 10, 2014 I had a similar issue with my Heritage Liberty. It buzzed and sounded raspy and distorted in a bad way ONLY after a lengthy warm up over 30 minutes. I had it at a tech for months, changing all pots, tubes, rebiased, speakers...still raspiness...but less...much less. The innards looked clean enough to eat off of. All connections checked out. Sometimes amps just do crazy things. If mine ever goes back to buzzy-raspy land, it's going straight to the best amp tech I can find. Meanwhile, the tone is sweet as it was on the first day of ownership. I hope you find out what's up with your Patriot. I think there might be a Paul C. gremlin haunting it. Have you called an exorcist? J.Kidding. Good luck with the fix. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.