Traynor Beta 800 testing

[g1]

What about the 5W 2.7k resistor in parallel and to the right of C10?

That is only in the later versions, I don't think his version has that (post #1 schematic), but he can confirm.

[JP-Stereo]

There is no 5W 2.7k...

At the right of C10 there are 2x 100ohm 1w resistor (R8, R9) between the +65v rail and Q1 collector.
R10 and R11 are 4.7ohm 0.5w between Q1 and Q2 emiters and the ground.
And 2x other 100ohm 1w resistor (R12, R13) between the -65v rail and Q1 collector.

I will swap ZD4 and ZD5 to see if the problem move and repace ZD3 for a new load tested one.

I figure only Q2 will be left at that point.
Or since Q1 is triggered by the negative rail via ZD5, is it this one that regulate the negative rail ?

[g1]

I'm attaching the complete service manual for the earlier versions. See 'Important' note on pg.9. It's possible Q1 or Q2 may have been damaged.
Suggest you connect the amp boards like x-pro suggested. The bulb limiter may be what is giving you trouble. A variac would be better. Follow the test procedure on pg.9 and 4 of 'SM'.

edit: adding 'SM2' manual containing some other info

[x-pro]

Or since Q1 is triggered by the negative rail via ZD5, is it this one that regulate the negative rail ?

No. Q2 regulate the negative rail.

[JP-Stereo]

I am still waiting for some new BD649 from a different source.
I should receive them this week.
Hoping they will not be leaky

Then i will try the written testing procedures.

[JP-Stereo]

I finally receive the transistors.
Both BD649 and BD650 from a different source and manufacturer than the previous leaky one.

Since Q1 (BD649) was leaky, i didn't trust it.
I fully tested a new one and NO LEAK, so i install it.

Now i have symetricaly wavy +65/-65v rails and R8 & R9 are overheating (smoke)...
With no load.

The transistors are not regulators.
As per the service manual, they are there to equalize the voltages of the rails at power off.

Maybe i should load this PS a little, but i do not want to expose the amp board at this point.
This power supply is far from conventionnal and kind of small for the amp that it is feeding.

Is a static load of around 10 to 25% of the full power a good idea ?

The other consideration is that there are 2 different power rails requiring different loads.

[x-pro]

The transistors are not regulators.
As per the service manual, they are there to equalize the voltages of the rails at power off.

How does the equalization process work?
By adjusting!

Is a static load of around 10 to 25% of the full power a good idea ?

It's worth a try.

[JP-Stereo]

I remove and retest Q1 and Q2 transistors.
I rechecked all the diodes and do a dynamic test on the 3v, 16v and 33v Zeners.
All were on specs exept ZD3 the 3.0v Zener between the two transistors that is providing 2.0v instead of 3.0v.
The original BZX79 has been replaced by an 1N5225B that may have more tolerance.
So i order the exact BZX79 as per the original design.

I also notice that the CLIP indicator circuit may load the +65v rail if defective.
I reinstalled ZD3 just to try without the LED board but it's not changing anything, R8 and R9 are still overheating.

How come this simple circuit is refusing to work ???

[x-pro]

Without power supply. First check the amplifier output to Common with a resistance meter. There should be no short circuits.
Run the amplifier through a tube as it should be when fully assembled, but without load or signal.
Measure the voltages: at the output of the amplifier, at all supply rails. Supply power to pins 7 and 4 of U1. Measure all voltages relative to the common.
I think the discharge circuit works well enough if everything inside is serviceable and there are no broken printed tracks.
If nothing has burned out within 5 minutes, then turn it on without the lamp. Again, measure the output voltage. Adjust the Bias.
Next, connect the generator in the standard way and check the output characteristic. Without load. Then with load.

[JP-Stereo]

Thanks for the procedure suggestion, but at the current time i do not want to involve the amplifier modules in the mix.
I need to get hold of the power supply unit first and once this one will behave correctly, then i will follow the procedures with the amplifiers.

I just have a hard time figuring the value of the "resistive load" to implement on the +/-80v and the +/-65v rails...
In order to operate the PSU in an acceptable mode.

[g1]

If you have a variac you can use the start-up procedure described in the service manual and you will not damage the amp modules. Why not do it that way?

[JP-Stereo]

I have a few considerations:
- The Power Supply as well as the Amplifier boards have all received many replacement components.
I am trying to proceed by step in order to avoid mixing different problems that may still exist on the different boards.

- The Power Supply have shown a good steady posifive rail, it should be able to do the same thing with the negative rail too.

- Now that i've replaced the leaky Q1, i have R8 and R9 that are smoking ...

I figure i have to adress this before feeding the amps

[x-pro]

Did you replace those resistors? What wattage are they? What is the voltage across the base of Q1?

[JP-Stereo]

R8 and R9 are still functionnal, i haven't let them heat long enough to burn, but they do have a tan...
1w each, two on both side.

For the measurment, is it Q1 base vs Ground ?

[x-pro]

For the measurment, is it Q1 base vs Ground ?

Yes.