Search found 20 matches

by GFT58
Mon Mar 08, 2021 1:10 pm
Forum: Guitar Amplifiers
Topic: Peavey VTX Classic troubleshooting help
Replies: 31
Views: 10569

Re: Peavey VTX Classic troubleshooting help

So I checked continuity between points from Q6/7 working my way back to Q4/5. It was either a bad solder joint and or broken trace between the emitter of Q6/7 and R126/130. I ran some jumpers and hooked everything back up then checked all voltages on the tube pins, Vi and Vk, and the power board. Al...
by GFT58
Sun Mar 07, 2021 2:08 pm
Forum: Guitar Amplifiers
Topic: Peavey VTX Classic troubleshooting help
Replies: 31
Views: 10569

Re: Peavey VTX Classic troubleshooting help

So I went ahead and pulled Q4/5 out and checked them and they tested fine. Then I pulled r123/124/128/129 and the all tested fine. So, at this point I'm at a loss for where to go next. Anybody have any ideas?
by GFT58
Sat Mar 06, 2021 7:27 pm
Forum: Guitar Amplifiers
Topic: Peavey VTX Classic troubleshooting help
Replies: 31
Views: 10569

Re: Peavey VTX Classic troubleshooting help

I found some info on using diode function of DMM to test parts out of circuit.
by GFT58
Fri Mar 05, 2021 6:01 pm
Forum: Guitar Amplifiers
Topic: Peavey VTX Classic troubleshooting help
Replies: 31
Views: 10569

Re: Peavey VTX Classic troubleshooting help

I've took a different DMM and rechecked the transformer readings and wah la they're where they should be. So I changed out Q4 and Q5 and turned it on. I could hear that there was noise coming from the speakers so I grabbed a guitar and low and behold I've got sound, albeit a little fizzy sounding. S...
by GFT58
Tue Feb 16, 2021 7:28 pm
Forum: Guitar Amplifiers
Topic: Peavey VTX Classic troubleshooting help
Replies: 31
Views: 10569

Re: Peavey VTX Classic troubleshooting help

So planning for a PT replacement I start searching for Peavey P/N# 705-18718 and 705-18348 and turned up zilch. What would you recommend if an OEM PT is not available Enzo?
by GFT58
Tue Feb 16, 2021 12:02 pm
Forum: Guitar Amplifiers
Topic: Peavey VTX Classic troubleshooting help
Replies: 31
Views: 10569

Re: Peavey VTX Classic troubleshooting help

No place but online to get parts so.... in the interim .. Enzo, I found these tests from GEOFEX to meggar the PT. I am a little confused on how perform these steps and want to do them correctly.
by GFT58
Mon Feb 15, 2021 7:54 pm
Forum: Guitar Amplifiers
Topic: Peavey VTX Classic troubleshooting help
Replies: 31
Views: 10569

Re: Peavey VTX Classic troubleshooting help

I had switched scales on the DMM. When I'm on the 200V range the readings are 183, I switched to read both taps to the higher range (500V) I got 303 but forgot to go back to the individual taps and retake. The individual taps are 151 on the higher range. Why the difference? I have no idea.
by GFT58
Mon Feb 15, 2021 6:22 pm
Forum: Guitar Amplifiers
Topic: Peavey VTX Classic troubleshooting help
Replies: 31
Views: 10569

Re: Peavey VTX Classic troubleshooting help

Readings were still 100V low with F1 removed and standby switch OFF. I'll check the website thanks Enzo, or taking it to the curb.
by GFT58
Mon Feb 15, 2021 3:25 pm
Forum: Guitar Amplifiers
Topic: Peavey VTX Classic troubleshooting help
Replies: 31
Views: 10569

Re: Peavey VTX Classic troubleshooting help

It looks worse and worse for this amp as I wait for parts. F1 blew yesterday, I replaced it and so far it has not blown again. My heater readings are down to 5.7VAC, where they were a consistent 6.3VAC. My DMM had a low battery so I posted some erroneous readings yesterday, I've re-posted today. To ...
by GFT58
Sun Feb 14, 2021 8:34 am
Forum: Guitar Amplifiers
Topic: Peavey VTX Classic troubleshooting help
Replies: 31
Views: 10569

Re: Peavey VTX Classic troubleshooting help

I took some more readings on the AC side of things on the power board. Seems I'm short of voltage there too.
by GFT58
Sat Feb 13, 2021 7:16 pm
Forum: Guitar Amplifiers
Topic: Peavey VTX Classic troubleshooting help
Replies: 31
Views: 10569

Re: Peavey VTX Classic troubleshooting help

So looking for replacement parts for Q4/5 I can find MPS6530 and 2N3904 both from Mouser. The 2N3904 was suggested from another forum. I don't have a clue what the difference is between the two of them. Enzo the readings I took from Q6/7 left legs were indeed in DC as you speculated. I did run the p...
by GFT58
Sat Feb 13, 2021 3:44 pm
Forum: Guitar Amplifiers
Topic: Peavey VTX Classic troubleshooting help
Replies: 31
Views: 10569

Re: Peavey VTX Classic troubleshooting help

I have a new set of tubes but I'm hesitant putting them in until I get a functioning preamp section.
by GFT58
Sat Feb 13, 2021 8:22 am
Forum: Guitar Amplifiers
Topic: Peavey VTX Classic troubleshooting help
Replies: 31
Views: 10569

Re: Peavey VTX Classic troubleshooting help

The Q6/Q7 measurements were taken as referred to in the attachment. If you were facing the front panel they were taken on the left left leg. At the time I ordered parts I hadn't considered replacing Q4/Q5. Not a good move. Thanks for the reply Enzo.
by GFT58
Fri Feb 12, 2021 9:07 pm
Forum: Guitar Amplifiers
Topic: Peavey VTX Classic troubleshooting help
Replies: 31
Views: 10569

Re: Peavey VTX Classic troubleshooting help

I've done some more research on other forums and found out some more readings to take. Q6 leg = 0.02 Q7 leg = 0.48 Junction of R119/C39 junction = 1.92 (R119 15v leg = 16.8V), R116/CR28 junction = 0.64, R127 = 1.27, R121/CR32 junction= 1.3, R136/CR37 junction = 1.05. The Q6 leg and R116/CR28 junctio...
by GFT58
Thu Feb 11, 2021 10:43 am
Forum: Guitar Amplifiers
Topic: Peavey VTX Classic troubleshooting help
Replies: 31
Views: 10569

Re: Peavey VTX Classic troubleshooting help

I replaced Q6 and Q7 with MJE15030G transistors, powered up the amp and F2 immediately blew. Replaced the fuse, powered up, F2 did not blow, and then took some readings: Vi - V1 = 3mV V2 = 28mV Vk - V1 = 88.4 V2 = 89.8 Plugged a guitar in no loud hum but no sound. I took some more readings and came ...