Avalon VT 737 sp

[punkt]

ok.
So if it fails the basic audio test, then we can check psu voltages. It’s been posted where one can do that previously.
If that is ok, then we can confirm tubes status. If tubes are ok.
Then the only thing left is the solid state bits and passive bits. Check for damage visually. Check the pots for damage as well.
At last resort, recap replacing sll
The 10uf and 100uf caps.
Or send it to me and I’ll fix it,

yea already done it, psu voltages seem alright, tube status should be also ok, got a fresh set of new tubes, changed the order, switcherood them, nothing helped, didnt saw any damages, have to get me a new screwdriver kit, because i dont have any fitting bit head for these screws that hold the pcbs.
so i will get this and take a look at the tubesocket etc


edit:
ordered an allen wretch set 0,5-3mm and these capacitors, will arrive on wednesday gonna update asap https://www.amazon.de/dp/B0CMQ8XQ4N?ref=ppx_yo2ov_dt_b_fed_asin_title

 

[TheseGoToEleven]

You might want to check the DC voltages coming out of regulators U2 and U4 on the main board. U2 should put out about -18V DC and U4 should have +18V. They supply power to a few opamps, including at least one that is always in the signal path.

Obviously be very careful not to accidentally short pins or IC legs together while taking measurements or you can create new problems.

If those are good then with a multimeter you can try measuring AC along the signal path to see where the level suddenly drops. Use the line input, set gain and output to +0 and don’t use the compressor or eq.

First check the AC signal level at solder point 17 on the motherboard. When using line input, this is where the signal first enters the gain knob.

Then measure the signal at solder points 16, 64, and 63. Finally, measure the signal at pin 15 or 16 of the I/O card (they are shorted), which is the card near the XLR jacks.

 

[punkt]

You might want to check the DC voltages coming out of regulators U2 and U4 on the main board. U2 should put out about -18V DC and U4 should have +18V. They supply power to a few opamps, including at least one that is always in the signal path.

Obviously be very careful not to accidentally short pins or IC legs together while taking measurements or you can create new problems.

If those are good then with a multimeter you can try measuring AC along the signal path to see where the level suddenly drops. Use the line input, set gain and output to +0 and don’t use the compressor or eq.

First check the AC signal level at solder point 17 on the motherboard. When using line input, this is where the signal first enters the gain knob.

Then measure the signal at solder points 16, 64, and 63. Finally, measure the signal at pin 15 or 16 of the I/O card (they are shorted), which is the card near the XLR jacks.

Hope i got the right U2 and U4, didnt saw anyelse, didnt got the requiered voltages at any measurepoint

 

[TheseGoToEleven]

You need to measure U2 and U4 on the main board, rather than the compressor card. They are mounted vertically behind the tubes.

 

[punkt]

You need to measure U2 and U4 on the main board, rather than the compressor card. They are mounted vertically behind the tubes.

Thanks, i get about 17+-

i cant seem to find point 17 - 16, 64, and 63.

it goes only up till t16
and the points 1-60 are cable connections to ports etc

 

[TheseGoToEleven]

Thanks, i get about 17+-

i cant seem to find point 17 - 16, 64, and 63.

+/- 17 volts is good, so no problem there.

Solder points 16, 17, 64, and 63 are located on the main board. They have wires connecting to the Gain and Output knobs on the front panel.

With Gain and Output both set to 0, the AC voltage measured at 16 should be about half of what it is at 17. And the AC voltage at 63 should be about half what it is at 64.

After the signal reaches 63, it gets amplified by tube V3 and then goes through the jumper J1 to the line I/O card (near the XLR jacks) on pins 15 & 16 (they are shorted together.)

 

[punkt]

+/- 17 volts is good, so no problem there.

Solder points 16, 17, 64, and 63 are located on the main board. They have wires connecting to the Gain and Output knobs on the front panel.

With Gain and Output both set to 0, the AC voltage measured at 16 should be about half of what it is at 17. And the AC voltage at 63 should be about half what is is at 64.

After the signal reaches 63, it gets amplified by tube V3 and then goes through the jumper cable J1 to the line I/O card (near the XLR jacks) on pins 15 & 16 (they are shorted together.)

+/- 17 volts is good, so no problem there.

Solder points 16, 17, 64, and 63 are located on the main board. They have wires connecting to the Gain and Output knobs on the front panel.

With Gain and Output both set to 0, the AC voltage measured at 16 should be about half of what it is at 17. And the AC voltage at 63 should be about half what is is at 64.

After the signal reaches 63, it gets amplified by tube V3 and then goes through the jumper cable J1 to the line I/O card (near the XLR jacks) on pins 15 & 16 (they are shorted together.)

Ok i got 2,6 ACV on 17 and 0,7ACV on 16, no readings on 63 and 64,

1,0 on Pins 15&16 if these are the right ones


do u mean pin 15&16 in the row of 20 ?

 

[TheseGoToEleven]

do u mean pin 15&16 in the row of 20 ?

Yes, I have put a red rectangle around them in this photo. And I shouldn't have said jumper "cable" since there is no actual cable, so I edited that out of my previous post so as not to confuse someone who might read it later.

 

[punkt]

Yes, I have put a red rectangle around them in this photo. And I shouldn't have said jumper "cable" since there is no actual cable, so I edited that out of my previous post so as not to confuse someone who might read it later.
View attachment 146066

Thanks, yea already meassured them only getting 1ACV

 

[TheseGoToEleven]

Ok i got 2,6 ACV on 17 and 0,7ACV on 16, no readings on 63 and 64,

There should definitely be readings on 63 and 64. Otherwise the signal is getting lost somewhere between 16 and 63. If the buttons on the front panel were all turned off, then as I recall the only things between 16 and 63 are the V2 tube amplification stage, some relays (all in default / de-energized position), and the Output knob.

1. Unplug the unit.
2. Measure the resistance between T12 and 64. (It should be zero.)
3. Measure the resistance between 63 and 64.
4. Measure the resistance between 63 and 62.

 

[punkt]

There should definitely be readings on 63 and 64. Otherwise the signal is getting lost somewhere between 16 and 63. If the buttons on the front panel were all turned off, then as I recall the only things between 16 and 63 are the V2 tube amplification stage, some relays (all in default / de-energized position), and the Output knob.

1. Unplug the unit.
2. Measure the resistance between T12 and 64. (It should be zero.)
3. Measure the resistance between 63 and 64.
4. Measure the resistance between 63 and 62.

T12 and 64. = 71 Measured at 20K OHM Setting of my multimeter
63 and 64.= 9,5
63 and 62.= 9,5

 

[TheseGoToEleven]

T12 and 64. = 71 Measured at 20K OHM Setting of my multimeter
63 and 64.= 9,5
63 and 62.= 9,5

Is that 71 ohms between T12 and 64? If it is 71 ohms and you measured with a 20k range, unplug the unit and measure again with a lower range like 200 ohms and it should be more accurate. Or if your meter has a continuity test, it should beep when the probes are touching T12 and 64.

For the other measurements, is that 9.5k ohms or just 9.5 ohms? If it is 9.5k ohms then the Output pot / knob seems fine.

Been a while since I used a multimeter without auto-range. Funny how you forget these things.

 

[punkt]

Is that 71 ohms between T12 and 64? If it is 71 ohms and you measured with a 20k range, unplug the unit and measure again with a lower range like 200 ohms and it should be more accurate. Or if your meter has a continuity test, it should beep when the probes are touching T12 and 64.

For the other measurements, is that 9.5k ohms or just 9.5 ohms? If it is 9.5k ohms then the Output pot / knob seems fine.

Been a while since I used a multimeter without auto-range. Funny how you forget these things.

No readings with a lower ohms range on t12

for the other measurements , dunno? i guess, sorry, this my first time ever doing stuff like this

 

[TheseGoToEleven]

No readings with a lower ohms range on t12

for the other measurements , dunno? i guess, sorry, this my first time ever doing stuff like this

Ok, I suspect your relays and Output knob are fine. Let's check whether signal passes through the V2 tube amplification stage.

Power the unit on again, make sure all buttons on the front are turned off (dark), wait 30 seconds or so for the "click" sound of the warm up relay, and then send signal through the line input. Measure the AC voltage at T11 and then at T12.

 

[punkt]

Ok, I suspect your relays and Output knob are fine. Let's check whether signal passes through the V2 tube amplification stage.

Power the unit on again, make sure all buttons on the front are turned off (dark), wait 30 seconds or so for the "click" sound of the warm up relay, and then send signal through the line input. Measure the AC voltage at T11 and then at T12.

T11 0,06
T12 5,3

 

[TheseGoToEleven]

T11 0,06
T12 5,3

Those measurements don't make sense. T11 is the input to the V2 amplifier, and T12 is the output. Your measurements would indicate that the signal was amplified nearly 100x, which can't be right.

What is your input to the Avalon? I would suggest a sine wave with a frequency well under 1k, like maybe 100 Hz, because otherwise (as mentioned earlier) your multimeter might get confused.

 

[punkt]

Those measurements don't make sense. T11 is the input to the V2 amplifier, and T12 is the output. Your measurements would indicate that the signal was amplified nearly 100x, which can't be right.

What is your input to the Avalon? I would suggest a sine wave with a frequency well under 1k, like maybe 100 Hz, because otherwise (as mentioned earlier) your multimeter might get confused.

1k hz sinewave at 0db +4dBU out
i measured in ACV, maybe thats the problem?
i will try again with a 100hz sinewave

4,5 and 0,05 for the 100hz sinewave

 

[punkt]

Tube Card is out, seems fine, resistors seem to be fine after checking with multimeter

Cant get the capictators out , the cables on the tube unit worked like charm with the copper thing, but no matter what i do (flux,incresing temp), these capacitators are really something else, advice woul be much appreciated

even tried 400degrees celsius

Update:

managed to get them out, but i cant get the solder off on the back

ordered a vacuum desoldering pump

 

[David Kulka]

Are you sure it's not just a bad or intermittent switch?

 

[punkt]

Tube Card is out, seems fine, resistors seem to be fine after checking with multimeter

Cant get the capictators out , the cables on the tube unit worked like charm with the copper thing, but no matter what i do (flux,incresing temp), these capacitators are really something else, advice woul be much appreciated

even tried 400degrees celsius

Update:

managed to get them out, but i cant get the solder off on the back

ordered a vacuum desoldering pump

Ok i changed all the caps on the 7374, plugged everything back in, forgotto put in the tubes and srarted the avalon
as soon as i turned on the power switch sparks came out the device, r19 on 7372 died, gonna replace the different caps and order a new resistor