3300 Series II lost output - main & headphone

[62vauxhall]

Got the transistor back in and you're right about those traces. If I'm to measure voltages with the power on, do I do that with the DMM set to DC volts or millivolts?

 

[NavLinear]

If you don't know what you are measuring you may want to begin with a higher (or the highest) range available on your meter - you can dial in the range based on the measured values you see. Have you verified the power supply voltages?

 

[laatsch55]

Gary, there is a 3300 Ser II manual in the archives for download....that might help.

DC millivolts...ground to the chassis..

 

[62vauxhall]

Nav, I took some measurements this morning but it was before I read your post. And yes, I don't know what I am measuring and don't know where to check for power supply voltage.

With the transistor back on the board and power turned on, these are the readings I just got:

DMM in diode mode
B to E - OL
B to C - .000
E to B - .658
C to B - .603
C to E - OL

DMM in DC volt mode
B to E - .000
B to C - OL
E to B - .000
C to B - OL
D to E - OL

DMM in DC millivolt mode
B to E - .0
B to C - OL
E to B - OL
C to B - OL
D to E - OL

Must leave for first shift of the day. Will return home briefly in about 5 hours and check for a reply.

 

[62vauxhall]

Gary, there is a 3300 Ser II manual in the archives for download....that might help.

DC millivolts...ground to the chassis..

Thanks. I'll take that measurement and look for that diagram when I get home in a few hours.

 

[62vauxhall]

I checked the transistor following your direction - DMM set to DC millivolts and ground (black) to chassis ground.

At transistor E - OL
At transistor B - OL
At transistor C - minus (-)OL

Then with the meter to volts
At transistor E - 18.4
At transistor B - 18.4
At transistor C - minus (-) .447

The schematic made me think to check R9 and D6 which also yielded 18.4 volts except one side of D6 which was 18.6.

 

[laatsch55]

Turn it off , plug in a signal source and select that source and put your meter on AC and look at the schematic And check The signal before and after those transistors
.

 

[62vauxhall]

I needed a nap before starting the afternoon shift.

I had the unit off and plugged a discman into AUX with a CD playing.

The meter is set to AC and the readings I got from the emiiters and collectors (if that's what you meant by before and after) of Q103 & Q203 was .003 volts.
Q1 collector fluctuated in the .018 to .031 area but was most often around .020 - it did not stabilize. Q1 emitter stabilized at .009 more or less.

Should the unit have still been off when taking these readings?

If the measurement points were to be other than those, are you able to identify by component number where they should have be taken?

 

[laatsch55]

Yes. I'll tell you when I get home..

 

[laatsch55]

Gary, jack up the volume on the pre amp about halfway with the input source and the preamp on. Set dmm to AC volts. Negative to ground on chassis. Positive lead to the upstream side of R132...see what ya got....

 

[laatsch55]

Have the source playing something...

 

[62vauxhall]

Upstream meaning the end of R132 that's closest to the rear jacks?

With source playing and preamp volume at 1/2, DMM set to AC and black lead to chassis ground

The reading at R132 as described above fluctuated around .04 volts.
The resistor's opposite end (closest to to the front panel) fluctuated more widely from a low of ~.017 to ~.10 but was mostly within the .02 to .05 range.

EDIT: Sorry to prolong this but I've got to get to sleep now in order to get up in 5 hours. I'll follow up on anything further you suggested between shifts tomorrow morning - about 10:30 Pacific Time.

 

[laatsch55]

Turn everything off, switch the op amp from the phono section to the one closest to the volume pot. The phono section is on the left towards the back. Then turn everything on again and make the same check...

 

[laatsch55]

Sounds good Gary..

 

[62vauxhall]

Thought I'd take that measurement before I left for the morning.

I noticed that that the op amp in the phono section is oriented opposite to the other three. The little notch on the edge of that one is closest to the rear jacks whereas that notch on the others (which are nearer the front) is closest to the front panel.

I assume that is correct because the preamp worked when I first got it so I made sure they went in the same way I took them out.

The AC voltage at the end of R132 closest to the back panel continues to be variable but in the .02 to .04 range. At the end closer to the front it's in the ~.014 to ~.020/.030 range.

Do these readings vary because the signal is music and not a steady tone? I have a 30Hz tone on a CD to re-cone speakers, would it be preferable to use that instead?

 

[laatsch55]

Yep. Did you check D6?

 

[62vauxhall]

No, just R132. I will be able to check D6 in about 5 hours.

So a music CD is satisfactory - no need to use that steady 30Hz tone?

 

[laatsch55]

Do you have the tone controls flat?

 

[laatsch55]

A test tone would be better. By having the tone controls flat you bypass the other op amp. That pre should output 1.75 volts at half volume.

 

[62vauxhall]

Using that 30Hz test tone CD, with preamp on, volume at halfway, tone controls flat at mid position, DMM at AC volts, the reading at both ends of R132 is .123 volts.

Either end of D6 produced .01 AC volts.