[morzh]

Why would you get any voltage on the cap feeding the tweeter?

[Diverted]

Sorry Morzh, you will have to bear with me. I assumed there would be voltages going to the tweeter. A lot of this troubleshooting is somewhat new to me; the complexity of this set is ...
What I need to figure out is why there's no voltage going to the driver tube (6F6), and what other problems there may be in the power supply.

[morzh]

The secondary side of any audio output xfmr will ALWAYS have 0V DC. Right now you are measuring DC.

Now as for the 6F6, if you have no plate voltage it means you probably have no voltage on the wire marked Black of the primary of the interstage transformer that it drives, or it is open.


PS. there are problems with Nostalgia Air so nosch access.
If you have the working link or scanned sch somewhere, post it, or it is difficult.

[Diverted]

Thanks Morzh. Correct on that. No voltage on the interstage primary. It's not open; reading about 185 ohms. Spec calls for 475 but this difference was discussed further up in the thread; others who had Heyboer make new interstages for them noted the same issue; thicker gauge wire.

Working now to shoot/upload some scans of the schematic. Thank you.

[morzh]

https://images.campyent.com/sites/defaul..._pg9-2.png


See if the choke coil 172 is good (continuity, 470 ohm). Or measure volts on both ends.

[Diverted]

Here's two photos of the pertinent part of the schematic. Sorry for the pink lines; those are areas I'd traced during recap and going over everything.
Thank you!

[morzh]

Read my previous post, check what's asked there.

[Diverted]

You wrote: Once you have established the B+ power and your filament voltages are OK (easily detectable), start mapping voltages across the tubes.

OK, filament voltages check; 5v on the rectifiers, 6v elsewhere.

You wrote: It is normal for anodes of most tubes to be at high enough voltage (100V-250V, or a bit more in case of audio output ones), the screen grids should be also fairly high, almost equal or a bit less than anode voltages, control grid is at low DC potential, and Suppressor grid is at Cathode potential.


Absence of Anode voltage is a good indicator of the load open, like the primary of an interstage RF/IF transformer.

This. Voltage on the 6L6 power tubes, but none on the 6F6 or 6J5. This is a good indicator of an open interstage primary. But I’m getting continuity across that primary, and just got it back from Heyboer.


You wrote: Start your check with pulling the rectifier and checking the AC outs.

Done. Getting about 340VAC on one transformer HV secondary, about 280 on the other. No voltages on this schematic so I don’t know if that’s correct. 

You wrote: Power down.

Then measure the load across the rectifier output, check if short is present.

No shorts, far as I could see. 

You wrote: If not, put rectifier in, put the loads (speakers) in, power up, briefly see if the DC develops and where it goes, once reached about 500V it should go down a bit and stabilize. Watch for smoke.


No smoke. Voltage starts at about 530, slowly tapers down to about 330 (reading this on the 6L6 outputs).

You wrote: Power down AND watch the DC going down. If very slow, you have no load. If fast (second or few) - OK.

Goes down pretty quick.

You wrote: Once this is OK, start measuring voltages.

Done. No voltage on the driver tube and 6J5.

You wrote :Check the transformers' continuities, check speakers.

Checked transformer windings, seem OK. Speaker field coil good, checked audio output transformer. All windings appear OK. Transformer 178 gets warmer to the touch after being on for extended period than 179, which stays cool.

[morzh]

No. I mean - the previous post to your last one at the time.

The post #20.


Try to read before you post. Or after. There might be posts you have missed.

[Diverted]

Oh, sorry Morzh. I must have missed that one.
I don't see Choke 172. On my schematic, part 172 is the tweeter field coil.

The two chokes I see in the power supply chassis are 167 and 175. Both check out and have the right ballpark resistance. Am I missing something?

[morzh]

Well, let it be the field coil, it is still a choke. Check it. Voltages before and after will do for now.

[Diverted]

OK, so I just checked from the black end of the interstage primary to the junction of the 2K resistor (Part 143) and chokce 175 .. If I'm looking at it right that should give me the reading across the tweeter field (670 ohms on the schematic). I'm getting an open here. No voltage on either end.

[morzh]

Didn't you say your 6L6 tubes do have plate voltages? If 175 is open and no voltage is present there 6L6-s would have none.
If 175 has no voltage on either end your rect tube could be bad. But then how do you get the 6L6 plate V?

In any case, you are pretty close so just check some wires and continuities.

[Diverted]

Sorry, let me rephrase. Trying to write this clearly, and not succeeding.

Choke 175 has continuity, and voltage at same level as 6L6 plates.

You'd asked me to check voltage and continuity across Part 172, the tweeter choke. I attempted to, measuring from the black primary lead to the junction of 143 and the choke 175. I tried and got no continuity. While I got voltage on the side containing the 2K resistor (part 143) I got no voltage on the other side (I measured from the black primary lead of the interstage.

Sorry if that was confusing.

[morzh]

Well your 172 is open. hence the problem. The field coil is bad.