67 Super Reverb ugly distortion

[vintagekiki]

I ran the 1000hz signal from the iPod thru input 1 channel 1, and measured with the scope and the multimeter across the speaker output, with the speakers connected. This is with the clip lead still connected to V1 P1 and the .001 capacitor.

[ATTACH=CONFIG]55546[/ATTACH]
Clear sine signal at 5.04V at 2.8 Ohm load. Power is 9W


I turned up the signal generator a little more until I saw clipping of the wave form

[ATTACH=CONFIG]55547[/ATTACH]
Softly clipping at 11.18V at 2.8 Ohm load. Power is 44W

I got no clear guitar sound when playing guitar thru channel 1, just hum.
Normal ch doesn't work because 0.047 from the anode (pin 6) is not connected to mix network 2 x 220k.
See previous atacements (red wire).

If these oscillograms are a signal source via .001uF to power amp they are fine.

Since you say that you did some mod on FSR, it would be best to compare the factory layout from schematic with your amp.

Please upload all modes that you worked at the FSR to see what's wrong.

EDIT 191012

- first the DC voltages for V1
P1. 298
P3. 2.42
P6. 254
P8. 1.9

All voltages are correct.

[earache]

Helmholz

Thanks for the reply and the help! I wanted to hear the output as well as see it, just to make sure my test equipment was working OK

[earache]

Vintagekiki

I'm very sure that the reverb on both channels mod I did back in 2011 are not the cause of this problem as this amp has been used \and gigged consistently with no problem since then (until just recently).

Thanks for the review of my tests so far. I have other work to do but hope to get back to this today or Monday

[Helmholtz]

Helmholz

Thanks for the reply and the help! I wanted to hear the output as well as see it, just to make sure my test equipment was working OK

I see. And if the speakers didn't produce ugly distortion during this test they are fine as well.

[vintagekiki]

... just to make sure my test equipment was working OK

Every test equipment was work OK, but ...

repairman is trying.

[earache]

Vintagekiki - from your previous post

“-Disconnect .001uF from mix network 2 x 220k and temporarily connect to test wire with anode (pin 1 normal ch ).
Turn on the guitar in normal ch and try the sound. ( I did this earlier and posted the results)
If the sound is loud and clear, test wire temporarily connect to g1 (pin 7) and try with a guitar”.

I played the guitar thru the speaker and it sounded good!

“If the sound is loud and clear and tone and volume controls works, test wire temporarily connect to anode (pin 6) and try with a guitar.”

I hooked up the signal generator and dummy load instead of the guitar and took three readings with progressively higher inputs:

[vintagekiki]

Vintagekiki - from your previous post

“-Disconnect .001uF from mix network 2 x 220k and temporarily connect to test wire with anode (pin 1 normal ch ).
Turn on the guitar in normal ch and try the sound. ( I did this earlier and posted the results)
If the sound is loud and clear, test wire temporarily connect to g1 (pin 7) and try with a guitar”.

I played the guitar thru the speaker and it sounded good!

“If the sound is loud and clear and tone and volume controls works, test wire temporarily connect to anode (pin 6) and try with a guitar.”

I hooked up the signal generator and dummy load instead of the guitar and took three readings with progressively higher inputs:

[ATTACH=CONFIG]55552[/ATTACH]

[ATTACH=CONFIG]55553[/ATTACH]

[ATTACH=CONFIG]55554[/ATTACH]

I don't understand why a persistent error when voltage measurement on a dummy load (level voltages are in the mV )
For 50W at 2 Ohm the voltage on the dummy load (speaker) is 10VAC

So I insisted that you try the guitar to see if you would get a strong and clean tone on Normal ch.

Set Normal ch controls / Volume 5 - 7 / Bass 4 - 5 / Treble 5 - 8 / Bright sw OFF
Plug guitar into Normal ch and play.

Is it sound loud and clear when:
a) test wire temporarily connect to anode (pin 6)
b) test wire temporarily connect to .047uF (red point X)

Question: Dummy load is connected to the spkr jack (white wire). Where did you connect the DVM and scope?

[earache]

Vintagekiki

When I connect between pin6 and .001 cap - loud and clear - see video here

https://www.dropbox.com/s/l4rtryijbx..._0127.MOV?dl=0

Same when I connect to point "X" - see video here

https://www.dropbox.com/s/ysqelyp1mu..._0128.MOV?dl=0

"Where did you connect the DVM and scope? " - I measured across the output jack

[vintagekiki]

When I connect between pin6 and .001 cap - loud and clear - see video here

https://www.dropbox.com/s/l4rtryijbxsyc0f/IMG_0127.MOV?dl=0

Same when I connect to point "X" - see video here

https://www.dropbox.com/s/ysqelyp1muicx37/IMG_0128.MOV?dl=0

In both cases, you have a strong and healthy tone on Normal ch.
I don't understand why it says "ugly distortion" when the tone is absolutely clean.

"Where did you connect the DVM and scope? " - I measured across the output jack

[ATTACH=CONFIG]55555[/ATTACH]

OK from the previous pictures because of the levels in mV, I couldn't conclude where the DVM and scope were actually connected.

Do you now have a powerful and clean sound when you plug and play guitar into Normal ch or Vibrato ch inputs?

[earache]

Vintagekiki

The sound is Powerful and clear thru the Normal channel.

I have not tried the Vibrato channel. We were testing thru V1.

It seems we haven’t come to the bad component yet.

What do you suggest we do next?

Also - I’ve learned so much already, thanks for all the help so far!

[Helmholtz]

Correct me if I am wrong, but meanwhile we found that:

- the power stage including OT is fine
- speakers are fine
- Normal channel is fine

Does the Vibrato channel still produce ugly distortion? Just asking because symptoms caused by bad mechanical contacts (jacks, tube sockets) sometimes "disappear" during test/repair.

BTW, does the Vibrato effect work? It shouldn't according to your V5 voltage measurements. Could be a bad tube.

[vintagekiki]

The sound is Powerful and clear thru the Normal channel.
What do you suggest we do next?

Vibrato ch check step by step
Put in socket second and fourth tube (12AX7)
Set Vibrato ch controls / Volume 5 - 7 / Bass 4 - 5 / Treble 5 - 8 / Reverb 0 / Bright sw OFF

Plug guitar into Vibrato ch and play.
Does volume and tone controls work?
Is it sound powerful and clear or ugly?

[vintagekiki]

About Fender signal test voltages

[earache]

So it looks like I might have a set back here.

I set up the latest test as Vintagekiki described, by putting in V2 and V4 tubes, and playing thru the "Vibrato" channel with controls at 5, reverb and vibrato off.
The test lead is still connected from point "X" to the .001 capacitor.

The setback, is that I'm now getting some of that distortion upon heavy attack of notes.

Perhaps it's because no one is home right now and I'm hitting the notes harder...

I switched back to just having V1 in place and connecting the test lead from P6 V1 to the .001 cap and still the distortion is there upon heavy attack, playing thru "Normal" channel.

i checked the speakers for voice coil rub but it didn't seem like there was any.

I am out of time for today, but the first thing I will do tomorrow is check the output jack and make sure that the ground connection to the chassis is good.

[earache]

VK - the Fender schematic you posted is much more recent, do those voltage settings still apply?