oscilloscope info

[bsco]

Looking for some info on a Brunelle model 2988 oscilloscope....Contacted the manufacturer but where the scope is so old, they no longer carry any info on it.......I also scoured the net and still came up dry.......I am trying to find out what is the maximum dc voltage it can safely measure.....when working on vacuum tube circuits you have to measure ac voltages on a dc level....and the dc levels are much higher than solid state amps....so I was wondering if somebody out there in repair land had one of these scopes and had some info on it.....I may have posted this in the wrong place and if I have then please advise.....
Cheers,

[g1]

If by any chance it looks exactly like this, there should be owners and service manuals available under Elenco or Meguro MO-1251
Meguro MO1251 日本目黑 二手示波器

[bsco]

Yes....it looks like the same scope....thanks for that info....I'll check out those brand names you mentioned.
Once again thanks very much...
Cheers,
Bernie

[g1]

Looks like the service manual may be very hard to find or not available, user manual here:
Download Elenco Electronics MO-1251 User Manual

[bsco]

I found the user/service manual at Elenco......seems to be the exact same scope....Thank you very much.....Really appreciate it....
Cheers.....
P.S. Actually g-one the link you provided is the user/service manual.....

[g1]

Can you post the link to the manual you got?

[bsco]

Looks like the service manual may be very hard to find or not available, user manual here:
Download Elenco Electronics MO-1251 User Manual

If by any chance it looks exactly like this, there should be owners and service manuals available under Elenco or Meguro MO-1251
Meguro MO1251 日本目黑 二手示波器

Actually, both of those links you gave me will get you the same manual...I downloaded it from Merguo and I went in after and checked on your second link, the one from Elenco and it was the same manual...Complete with operating instructions, circuit descriptions and adjustments, parts lists and schematics and printed circuit layouts...It's everything in one...the way a manual should be.... I have a question for you....I know that if you have a vacuum tube amp with more than one set of output tubes, you can run the amp with only one tube per side....will that work with an amp that has 12 output tubes?? or six sets of two??? and each set has it's own biasing adjustment independent of the other sets...maybe i should post this to a new thread....but anyway, I figured I'd ask you seeing as how i am here now.....
Cheers,
Bernie

[g1]

Ok, I thought you maybe found it on the Elenco site and I didn't see it there so I was a little confused (or more ).

Hmm, 12 output tubes, YBA-300?
Yes for testing you can just run a single pair. For actual use, you can get into some pretty big impedance mismatches if you are going from 6 pair down to 1 pair. 2 pair down to 1 pair is usually considered acceptable mismatch, same as mismatching by one impedance step at the secondary side of OT.
A second consideration is B+. Going from 6 pair power tubes down to one pair is going to raise the B+ a fair bit. Depending on the voltage rating of the filter caps, they could be endangered.

[bsco]

Ahhh...you know the amp.....Yeah...it has this low level hum when it is turned on....it plays fine....but when you stop it has this hum coming from the speakers.reminds me of the hum you get when the bias is off in an Ampeg SVT....and the level is not adjustable...I removed the pre amp tubes to see if one of them were causing the problem...then I removed one pair of output tubes at a time but same thing....I might have a mis-match in more than one set of tubes.....there are two caps in the supply rated at 350V.....the rest are rated at 450V....sounds like it is not a good idea.....unless I measure the B+ each time i remove a set to see what the change is going to be....anyway thanks for the advise....it.s got me thinking.......
Cheers,
Bernie

[g1]

Best to start a new thread, may be easier for others to find it in the future if it has the model in the title.

[bsco]

I was thinking that after the fact....I was talking to uncle Guy after and the amp can run no problem on only one set of tubes....I'll start up a new thread on this and post what I found....One pair of tubes and two screen resistors...
Cheers,
Bernie