Avalon VT 737 sp

[pucho812]

I am racking my head on this.

are all the polarized caps in the same direction? It's something that goes unnoticed but to tie into my statement of striving for perfection, just about every lytic in an avalon piece will face the same direction of polarity.

lets reassemble the unit was far as all the cards in it, and all the wires soldered back into place. double check the wires for the tube sub board. also double check any daughter card you pulled out to make sure they are installed correctly, I.E. not missing a pin or off by one pin.

 

[punkt]

I am racking my head on this.

are all the polarized caps in the same direction? It's something that goes unnoticed but to tie into my statement of striving for perfection, just about every lytic in an avalon piece will face the same direction of polarity.

lets reassemble the unit was far as all the cards in it, and all the wires soldered back into place. double check the wires for the tube sub board. also double check any daughter card you pulled out to make sure they are installed correctly, I.E. not missing a pin or off by one pin.

yea yesteday i detected a missing cap on the eq card, that i forgot to solder back on, fixed that, but problem remains, i mean it worked for 1,5 weeks without that one cap

did everything u said already 2 times, but nah, nothing
i used the avalon everyday for the last 1,5 weeks and then suddendly after going to bed and switching it back on the next day, nada, nothing, back to square one

i also checked all the resistors on the tube board, the measurements have been fine

i wonder if @TheseGoToEleven has an idea

​

 

[pucho812]

yea yesteday i detected a missing cap on the eq card, that i forgot to solder back on, fixed that, but problem remains, i mean it worked for 1,5 weeks without that one cap

did everything u said already 2 times, but nah, nothing
i used the avalon everyday for the last 1,5 weeks and then suddendly after going to bed and switching it back on the next day, nada, nothing, back to square one

i also checked all the resistors on the tube board, the measurements have been fine

i wonder if @TheseGoToEleven has an idea

​

There are a lot of parallel paths in the unit especially on the main board, it helps keep the noise floor way down.
As always you can send it to me and I will get it sorted FOC, just cover the shipping.

 

[punkt]

There are a lot of parallel paths in the unit especially on the main board, it helps keep the noise floor way down.
As always you can send it to me and I will get it sorted FOC, just cover the shipping.

thanks for the offer again, but i have to politely decline due to the immensive shipping cost from germany to the usa

any tips tho? ._.
like what are the next steps of diagnosing

since the signal leaves v1 and v2 cant we narrow down the issue?

 

[pucho812]

thanks for the offer again, but i have to politely decline due to the immensive shipping cost from germany to the usa

any tips tho? ._.
like what are the next steps of diagnosing

since the signal leaves v1 and v2 cant we narrow down the issue?

yes you are correct, sorry I keep forgetting you are Europe.

Well if it's V1(input tube) V2(eq tube), V3(output) is next.

 

[punkt]

yes you are correct, sorry I keep forgetting you are Europe.

Well if it's V1(input tube) V2(eq tube), V3(output) is next.

what and how to check there

 

[TheseGoToEleven]

since i got those readings
2,8 on t8 0 on t9
100hz sinwave through instrument input

100hz sinwave -20db through mic input
3,3 t8
0,1 t9
t11 0,9
t12 6,3

i assume v1 and v2 are fine since the signal is leaving but no readings on the output points 6x

Yes, these measurements show that signal is getting amplified by tubes v1 and v2, so those tubes seem fine. Check readings at T13 (input to tube v3) and T15 (output of tube v3).

If the signal at T14 looks ok, then the next step in the signal path is the circuitry on the 7372 IO card that takes the unbalanced audio signal coming from v3 and converts it to a balanced audio signal to send to the XLR jack. Measure AC on these pins on jumper J1 of the 7372 card:

7372 pins 15/16: The unbalanced signal coming from v3 (should be same as T14).
7372 pins 17/18: The "positive/hot" side of the balanced output signal.
7372 pins 19/20: The "negative/cold" side of the balanced output signal.

 

[punkt]

Yes, these measurements show that signal is getting amplified by tubes v1 and v2, so those tubes seem fine. Check readings at T13 (input to tube v3) and T14 (output of tube v3).

If the signal at T14 looks ok, then the next step in the signal path is the circuitry on the 7372 IO card that takes the unbalanced audio signal coming from v3 and converts it to a balanced audio signal to send to the XLR jack. Measure AC on these pins on jumper J1 of the 7372 card:

7372 pins 15/16: The unbalanced signal coming from v3 (should be same as T14).
7372 pins 17/18: The "positive/hot" side of the balanced output signal.
7372 pins 19/20: The "negative/cold" side of the balanced output signal.

0,9 on t13 no readings on t14

i get 1,0 on pins 15/16 tho
no readings on 17/18, 19/20

i guess i have to desolder the tube plate again?

 

[TheseGoToEleven]

0,9 on t13 no readings on t14

i get 1,0 on pins 15/16 tho
no readings on 17/18, 19/20

i guess i have to desolder the tube plate again?

No, I don't think so. And I'm sorry -- the output of v3 is T15, not T14. I'll correct my earlier post. Please confirm that you have an AC signal at T15.

 

[punkt]

No, I don't think so. And I'm sorry -- the output of v3 is T15, not T14. I'll correct my earlier post. Please confirm that you have an AC signal at T15.

yup i get 1,0 on t15,

 

[pucho812]

yup i get 1,0 on t15,

oh really. what if you had a bad output pot or lost a connection on the output pot?

 

[punkt]

oh really. what if you had a bad output pot or lost a connection on the output pot?

i dont think so, because we already checked the output pot and most importantly the meter doesnt react, it does when i crank the signal up, but yea, i think it gets lost somewhere before it goes to the output pot, i might be wrong because u guys clearly have more expierince but yea

 

[pucho812]

i dont think so, because we already checked the output pot and most importantly the meter doesnt react, it does when i crank the signal up, but yea, i think it gets lost somewhere before it goes to the output pot, i might be wrong because u guys clearly have more expierince but yea

easy enough to check. probe it. you will see solder point from the main board going to the pot. Probe those points.

 

[punkt]

easy enough to check. probe it. you will see solder point from the main board going to the pot. Probe those points.

u mean point 62-65 ? no readings

i think these are the righ ones, because these are connected via cable to the output knob

 

[pucho812]

u mean point 62-65 ? no readings

i think these are the righ ones, because these are connected via cable to the output knob

Yes I ment those point.
Yes you should be seeing signal there. normally. Especially if you are testing with a sine wave or other constant sound source.

Let me think somemore

 

[punkt]

Yes I ment those point.
Yes you should be seeing signal there. normally. Especially if you are testing with a sine wave or other constant sound source.

Let me think somemore

maybe there should be a very small signal coming out, because there is some signal passing thorugh the output, but its very quiet barley hearable without cranking everything up, but my multimeter isnt sensitive enough, @TheseGoToEleven pointed this out in an earlier stage of testing, doing the same measurments

but then i recapped that badboy and it worked again for 1,5 weeks xD, but it worked relentlessly tho

 

[TheseGoToEleven]

u mean point 62-65 ? no readings

i think these are the righ ones, because these are connected via cable to the output knob

Are your output knob wires really numbered 62-65? Or are they 61-64?

 

[punkt]

Are your output knob wires really numbered 62-65? Or are they 61-64?

61-64 my bad

 

[TheseGoToEleven]

61-64 my bad

Ok, so 61 and 62 should always be zero.

When the compressor and eq buttons are turned off, 64 gets the output of tube stage v2, so it should measure the same as T12. It should never be zero.

63 is the wiper of the output pot/knob. When the knob is turned all the way clockwise, it should be the same as 64. When the knob is set to the middle (0db), 63 should be half of 64. (If I remember correctly.)

63 is what gets sent to the input of tube stage v3, after it passes through capacitor C29. So it should never be zero either. Though your meter might think so.

 

[punkt]

Ok, so 61 and 62 should always be zero.

When the compressor and eq buttons are turned off, 64 gets the output of tube stage v2, so it should measure the same as T12. It should never be zero.

63 is the wiper of the output pot/knob. When the knob is turned all the way clockwise, it should be the same as 64. When the knob is set to the middle (0db), 63 should be half of 64. (If I remember correctly.)

63 is what gets sent to the input of tube stage v3, after it passes through capacitor C29. So it should never be zero either. Though your meter might think so.

just tested again, nope no readings on 63 or 64 whatsoever even when cranking up gain and output and t12 readin 13, no readings on 63&64

just saw that on the tube card c5 and c4 are flipped upside down, never touched these ones, is this normal?