Avalon vt-737sp

[Jdm5149]

Previous tech markings getting -13.76v on left wire No voltage on right wire

 

[Jdm5149]

now it reads -3v on left grey wire to meter

 

[Jdm5149]

Further testing. Turn unit on. Have unit upside down as in pic. Left grey wire to meter reads -14.8v. I engage meter button. Voltage goes to zero. Disengage button , voltage goes to -4

 

[pucho812]

4 is 16.38v. 7 is -18v.

Hmmmm. That should be ok. Usually when the needle pins hard to one side with no audio present, it means the opamp lost one of the bipolar supply voltages.

 

[Jdm5149]

It’s negative voltage. The way u explained it the voltages are reversed.

 

[Jdm5149]

I have -14 at the meter to start

 

[pucho812]

That meter ia not an Avalon meter.
Was that replace too?

 

[Jdm5149]

Gee don’t know. This unit seems to be a mess. Would voltages still matter.

 

[Jdm5149]

Purchased 4 pots. Gonna wait til then to work on unit. They do sell meters also but gonna hold off on that. Any other suggestions about meter and compressor troubleshooting would be welcomed. Lol

 

[Jdm5149]

K. Update. Got bulbs from autozone and they work but not right size. They don’t stay in. Will order those. Meter still pegs with switch disengaged. With signal or no signal going into it. But…. Seeing action on the compressor. Sending tone thru 737 into my console I can get my console meter to somewhat hit -10 and -3. But I definitely see reduction when playing with threshold and compression. I see also that the preamp gain really needs to push the compressor. And like said the compressor reacts very slowly. Maybe the mod will help but I kinda like the mu style reaponse. K. Just waiting on pots. Maybe the only main issue left is the meter. It does zero out with switch engaged and responds to compression. But like said before, with meter switch disengaged it just pegs. Maybe the trim pot?

 

[kags]

Have you, by any chance, verified that your pots are not wired backwards? That would create unexpected behavior of the compressor, especially a molasses-like release. Since your replacing pots anyways, be sure to verify the wiring.

 

[pucho812]

man whoever was previous tech on this really did a number of things that are just baffling.The meter can fail due to people knocking the glass loose in the meter cover causing it to r4est against the meter which eventually fails from not moving when it should.

Why they would replace the meter and wiring with anything other than what Avalon uses is odd. Avalon uses Sifam meters. That meter while labeled in VU on the scale maybe something else entirely. The VU the wiring is fine but, it's not the same color code which avalon uses specifically to make it easier to service. You will also note things like how all the lyrics face the same direction, again to make it easy for servicing.

Can you film a video of the unit in action and share?
You don't need to do anything fancy Just have a line level sine wave of 1K @ +4 and show us the unit in action. I would love to see the meter and what it is doing VS what is getting described.

 

[Jdm5149]

Will do. Maybe Saturday or Monday. Pots are arriving tomorrow hopefully.

 

[Jdm5149]

K. 1k at 4db going into line in.
View attachment IMG_5940.mov

 

[pucho812]

Have you tried to flip the meter leads and see if it pegs the other direction?
There is very little going on in the metering circuit.
As mentioned there is that op07 chip near the XLR connections that feed the meter.

Maybe the chip is bad?

 

[Jdm5149]

I know the voltages are reversed as to how you say they were supposed to be. But the meter seems to work when button is engaged. Correct ?

 

[joeblack007]

Thanks a lot Pucho812 for all your tips and explanations! I have no problems with my Avalon 737 at the moment, but this discussion may be very useful later in case of trouble or if I need calibration. All this sharing of your knowledge is very much appreciated

 

[Jdm5149]

 

[Jdm5149]

Got the pots but they sent wrong bass eq knob. Also I realized the prior tech/owner really bastized this unit. The attack and release pot are basic guitar size pot. They drilled out cover plate and frame to fit. Have to fill gap with washer I guess. Would the wires be connected same way as these. The are 3 pin.

 

[pucho812]

Every time you post more photos my heart breaks. No wonder you got it so inexpensively.