Traynor YCV40 Issues

[stereomonostereo]

Hey guys,

Working on a Traynor YCV40 that had a blown Q1 LM7824 voltage regulator. I replaced the component, and then found that U2 has also blown. I replaced that as well, and then powered the unit up on a current limiter. First off, the Standby switch is functioning to the extent that it's switching the Red and Yellow LEDs, but not turning off the B+ voltage. I'm also not getting any negative voltage at U1 or U2.

The limiter bulb starts out dim, but as the power tubes warm up it gets bright. Brighter than it should. On my bias meter i'm seeing 25mA.

It appears to me like there's a bad diode affecting the negative voltage to U1 and U2, but the diodes all seem to test okay. In the past i've had them test out well but end up being the problem anyway. I've attached a link to the service manual. Is anything popping out at anyone? Thanks in advance for the help!

http://traynoramps.com/downloads/servman/sm_ycv40.pdf

[g1]

Is this the correct version schematic? There are several different versions with big differences in the stand-by arrangement.
On the one you linked, standby is just a mute that disconnects the power tube cathodes. The B+ does not get switched.

[g1]

Also, this version has the IC's running on +24V, so there will be no negative voltages. The V- supply pins will be grounded.

[stereomonostereo]

That's good to know, thanks. I was wondering about that missing negative. I found an older thread that talks about the standby issue, and suggests replacing IRF830 (Q8), the 1N5240 zener (D13), and 4N35M (U3). It doesn't explain why the U2 IC was blown, but once i get the parts in i'm going to give that a try

[g1]

So the schematic you linked is not the version you have?
Yours has the opto (U3) ?
You must have the exact schematic for your version or you will run into problems (and around in circles ).

[stereomonostereo]

Mine ha the U3 Optocoupler, yes. Looks like i'm hunting down a new schematic

[Jazz P Bass]

Looking at the schematic, I do not see a V- supply , as such.
The ic's (U1 & U2) pin 8 is attached to ground.

That +24Vdc supply is busy.
It appears to be the heater supply for V1 & V2, as well as the supply for the Ics & relays.

[Jazz P Bass]

Here is the schematic with U3 optocoupler.

TraynorYCV40.pdf

The one posted by the OP should be relabeled to read "Traynor YCV40/T".

[g1]

Even with the opto, there are several versions. And service bulletin/updates.
Best bet is to contact Yorkville with the model and serial number and ask for the correct version schematic.
Depending on which country you are in, use the appropriate "product/service questions" email address on this page:
Traynor Amps

[stereomonostereo]

I emailed Traynor about a week ago and i'm waiting on a response. I just replaced D13 and U3, and the standby circuit is back in working order. I still have the amp running on the limiter and when i take it off of standby it lights the bulb up pretty bright and there's an audible hum from the speaker. With the power tubes pulled, the limiter is dim.

With the power tubes pulled i'm getting 403 at the plate, 396 at the screen grid, and -7 at the control grid. It seems to be localized with the power tubes, but my voltages don't seem too off. Do they?

[g1]

The bias voltage at the control grids is not right. It should be much more negative, maybe -40 to -50V range.
That is why the tubes are over-conducting and the limiter lamp is going bright.
Something wrong in the bias or auto-matching circuit.
But the bias circuit may not work right without the tubes so it may be a bit tricky.

[stereomonostereo]

Also, I powered up the amp off of standby without the limiter just momentarily, and the bias meter starts to fly away. It looks as if it's something with the bias circuit.

[g1]

On the schematic, above the power transformer is shown the raw bias circuit.
With power tubes removed, what do you measure at the point labelled -bias ?

[stereomonostereo]

I was getting -25, which was getting pulled down to about -5 by the time it hit the control grid. The circuit that i have is somewhere inbetween the two schematics. I replaced Q4 and Q5, and my voltage ended up being around -23 at the control grid. I fired her up and everything was okay with the power tubes, but the output was low and distorted. It seems U1 got taken out when U2 popped. I replaced that and she's working like she should.

Is this some sort of 'auto' biasing circuit? It sure confused the hell out of me.

[g1]

It's an auto-matching/balancing circuit.
The -23V at the grids still sounds off, but if you can get the idle current they spec., then it must be correct.
Should be 35mA per tube. The cathode resistors are different values for different versions, but you can just measure across them and calculate using whatever value resistors are in the amp. On the schematic from post #8, they have 10ohm resistors and you adjust the bias till you get 350mV across each resistor, for a current of 35mA per tube.
I think some versions may have 1 ohm, and some may even have 2 ohm there, but it could also be another model I'm thinking of.