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New Activity (
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Older Activity
Today,
02:32 PM
boroman
replied to a thread
Ampeg V4 wierd channel 1 & 2 interacting
in
Maintenance, Troubleshooting & Repair
Thank you guys. The story goes on: I have disassembled and cleaned Ultra Hi and Midrange switches, cleaned contacts and now I see how...
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43 replies | 642 view(s)
Today,
01:45 PM
Dark Mavis
replied to a thread
Cathode follower without elevated heater voltage
in
Theory & Design
Okay, so here are idle DC voltages for the preamp tubes and filter caps. Grid voltages were too small to measure accurately. I noticed...
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136 replies | 4917 view(s)
Today,
12:13 PM
m1989jmp
replied to a thread
Humdingers RULE!!
in
Maintenance, Troubleshooting & Repair
Yeah, had a 70s Twin Reverb come in with dead power tubes; after replacing filter and bias caps, still had ridiculous amount of hum. It...
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1 replies | 22 view(s)
Today,
10:52 AM
Gtr0
started a thread
Humdingers RULE!!
in
Maintenance, Troubleshooting & Repair
Hi Gang. I needed to drop a note on my latest experience with high'ish gain amp noise. Having built several high gain (and...
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1 replies | 22 view(s)
Today,
10:29 AM
vintagekiki
replied to a thread
Voicing Vox AC-30
in
Schematic Requests
https://reverb.com/item/29196508-schematic-diagram-package-for-jmi-era-vox-ac-30-4-and-ac30-6-amps-1960-through-1967 Read more... OS/056...
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12 replies | 7352 view(s)
Today,
08:26 AM
HaroldBrooks
replied to a thread
"Swirly" Distortion Decay Sound Fix !
in
Theory & Design
I think it would be considered a "grid leak resistor as it appears directly after the coupling cap, and is tied to ground. However... ...
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6 replies | 97 view(s)
Today,
06:21 AM
SoulFetish
replied to a thread
YADTMI - yet another dual triode mixing idea
in
Theory & Design
No doubt, I just forgot to draw the coupling cap. So I did a little more work. According to the info provided by the datasheet, the...
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6 replies | 161 view(s)
Today,
05:58 AM
Jazz P Bass
replied to a thread
Mackie SRM450 V3 schematic request
in
Schematic Requests
Hey, Rajan. Got anything to contribute?
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2 replies | 77 view(s)
Today,
05:16 AM
Chuck H
replied to a thread
Voicing Vox AC-30
in
Schematic Requests
You asked ;)
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12 replies | 7352 view(s)
Today,
05:07 AM
Chuck H
replied to a thread
Fender Blackface Deluxe Reverb Hum/Buzz problem
in
Guitar Amps
It would be fun to have the audio of that ;)
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14 replies | 200 view(s)
Today,
04:03 AM
drewl
replied to a thread
GK 1001RB got dropped, now random noise comes & goes
in
Maintenance, Troubleshooting & Repair
Considering all the weird problems I've encountered with these due to intermittent preamp PC board connections, I think that might be the...
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6 replies | 112 view(s)
Today,
02:24 AM
Randall
replied to a thread
Fender Blackface Deluxe Reverb Hum/Buzz problem
in
Guitar Amps
I did something this week while re-capping a AA165 Pro Reverb. While pulling the old 20uF filter caps at the same time, which I don't...
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14 replies | 200 view(s)
Today,
01:01 AM
pdf64
replied to a thread
Mesa Dual Rectifier Maverick -- DC on input
in
Maintenance, Troubleshooting & Repair
Some 12AX7 have a higher than desirable degree of (usually positive) grid current, an operating point with very low plate voltage seems to...
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9 replies | 91 view(s)
Today,
12:47 AM
drewl
replied to a thread
Mesa Dual Rectifier Maverick -- DC on input
in
Maintenance, Troubleshooting & Repair
I've seen bad cathode caps do weird stuff like that. Can't hurt to try.
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9 replies | 91 view(s)
Today,
12:30 AM
dmeek
replied to a thread
GK 1001RB got dropped, now random noise comes & goes
in
Maintenance, Troubleshooting & Repair
I don't advise shorting out Q4 & Q5, since you need their Vce drops to power Q2/Q2A. The 555 timer IC generates the delay-turn-on, which...
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6 replies | 112 view(s)
Yesterday,
11:50 PM
Chuck H
replied to a thread
"Swirly" Distortion Decay Sound Fix !
in
Theory & Design
I think I may need some clarity. 270k would be very high for a "grid resistor" but very typical for a "grid leak resistor". And "grid...
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6 replies | 97 view(s)
Yesterday,
11:41 PM
vintagekiki
replied to a thread
Voicing Vox AC-30
in
Schematic Requests
https://www.youtube.com/watch?v=oQud4emaSek Vox Pop - The Story of Dick Denney and the AC30 amp ...
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12 replies | 7352 view(s)
Yesterday,
11:35 PM
nevetslab
replied to a thread
GK 1001RB got dropped, now random noise comes & goes
in
Maintenance, Troubleshooting & Repair
I don't advise shorting out Q4 & Q5, since you need their Vce drops to power Q2/Q2A. The 555 timer IC generates the delay-turn-on, which...
see more
6 replies | 112 view(s)
Yesterday,
11:27 PM
HaroldBrooks
replied to a thread
"Swirly" Distortion Decay Sound Fix !
in
Theory & Design
You may be onto it as well Helmholtz. I am running a "20W" OT, but I would think based on the sturdy power transformer, and the high plate...
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6 replies | 97 view(s)
Yesterday,
11:23 PM
HaroldBrooks
replied to a thread
"Swirly" Distortion Decay Sound Fix !
in
Theory & Design
Thanks Chuck, I will play with the values of the 6L6 tubes as you mentioned, I just may not use 150k owning to the fact of the .047uf caps...
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6 replies | 97 view(s)
Yesterday,
10:58 PM
Helmholtz
replied to a thread
Mesa Dual Rectifier Maverick -- DC on input
in
Maintenance, Troubleshooting & Repair
Strange. Have you also tried different tubes in V2? Does the instrument connected have active electronics? Just excluding the DCV comes...
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9 replies | 91 view(s)
Yesterday,
10:36 PM
xtian
replied to a thread
Mesa Dual Rectifier Maverick -- DC on input
in
Maintenance, Troubleshooting & Repair
DC is positive WRT ground, and yes, vanishes when no plug inserted (input jack is properly grounding the tip).
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9 replies | 91 view(s)
Yesterday,
10:21 PM
bsco
replied to a thread
Randall RG75/G3
in
Maintenance, Troubleshooting & Repair
I'm glad as well..The customer picked it up earlier this afternoon......and he was quite happy..... Cheers
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8 replies | 214 view(s)
Yesterday,
10:04 PM
Helmholtz
replied to a thread
"Swirly" Distortion Decay Sound Fix !
in
Theory & Design
I would think of OT core saturation caused by PI signal asymmetry (means net DC in the primary) and low frequency content. Only a...
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6 replies | 97 view(s)
Yesterday,
09:52 PM
Chuck H
replied to a thread
"Swirly" Distortion Decay Sound Fix !
in
Theory & Design
I think the swirly distortion must be crossover distortion resulting from the bias voltage increase at the cathode resistor with conduction...
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6 replies | 97 view(s)
Yesterday,
09:32 PM
Helmholtz
replied to a thread
YADTMI - yet another dual triode mixing idea
in
Theory & Design
Correct, I missed this path. It was just a general remark. As shown without coupling caps the grid will see (high) positive voltage.
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6 replies | 161 view(s)
Yesterday,
09:27 PM
xtian
replied to a thread
Mesa Dual Rectifier Maverick -- DC on input
in
Maintenance, Troubleshooting & Repair
Well, still can't explain the stray DC on the input, but my main issue, nasty hum, was coming from a bad solder joint on the Lead channel's...
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9 replies | 91 view(s)
Yesterday,
09:22 PM
Dave H
replied to a thread
YADTMI - yet another dual triode mixing idea
in
Theory & Design
There's a DC ground reference through the feedback resistor and output load resistor.
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6 replies | 161 view(s)
Yesterday,
09:21 PM
Helmholtz
replied to a thread
Mesa Dual Rectifier Maverick -- DC on input
in
Maintenance, Troubleshooting & Repair
Is the DC positive or negative wrt ground? I guess the voltage drops to zero without a plug inserted?
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9 replies | 91 view(s)
Yesterday,
09:17 PM
Helmholtz
replied to a thread
Mesa Dual Rectifier Maverick -- DC on input
in
Maintenance, Troubleshooting & Repair
Not much known about "secondary emission" in small signal triodes. What's your source of information?
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9 replies | 91 view(s)
Yesterday,
08:54 PM
alexradium
replied to a thread
Mesa Dual Rectifier Maverick -- DC on input
in
Maintenance, Troubleshooting & Repair
secondary emission is a byproduct of fairly low anode voltage ,especially on modern production tubes,if its annoying try add a 100n and...
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9 replies | 91 view(s)
Yesterday,
08:42 PM
Pedro Vecino
replied to a thread
Mesa Dual Rectifier Maverick -- DC on input
in
Maintenance, Troubleshooting & Repair
Yesterday exactly the same thing happened to me with a DC3. The volume of the guitar creaked a lot with the lead channel selected. I took...
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9 replies | 91 view(s)
Yesterday,
08:28 PM
Chuck H
replied to a thread
Cathode follower without elevated heater voltage
in
Theory & Design
That resistor is part of a short feedback loop. Probably to stabilize the circuit? Such loops appear elsewhere in the amp too I notice. Not...
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136 replies | 4917 view(s)
Yesterday,
08:17 PM
dmeek
replied to a thread
GK 1001RB got dropped, now random noise comes & goes
in
Maintenance, Troubleshooting & Repair
At least if you still have noise with the output stage out of the circuit. it will be narrow the search down. You could short out Q4 and Q5...
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6 replies | 112 view(s)
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