BWD 539A oscilloscope

[Bob Johnson]

Does anyone have a schematic for the above scope. My scope s'display is somewhere way off the screen to the right. Seems there is a dc component getting on the horizontal deflection plates but I do not have the pin outs for the CRT or a circuit to check!


Ah Ha! found a circuit diagram but I still need the pin out details for the tube?

 

[73's de Edd]

Sir Bob Johnson . . . .

It's in the book . . . .
And being on this page *****

That would be a DC level / balance problem in either the X 1 Pin 12 or X2 Pin 10 hoz deflection plates of the units Brimar D13-611 kine. Which in turn, could relate to their differential Q129 and Q130 hoz drivers circuitry, as is being located at the top right corner of the schema.
How well balanced are the + and -48V supplies ? In conjunction with the +110 supply.
What has ~ 40+ years done to them ?
( I correlate my time referencing, as to how long it has been, since I had last used an / its uL733 )
That voltage shift related to predriver Q128 and its earlier direct DC coupled circuitry would be most suspect. Plus having no leakage in diode pair D127-128.
The BF337 collector and emitter resistors will probably not be at fault.

TECHNO-REFERENCING *****

73's de Edd
.....

 

[Bob Johnson]

Yes I thought it would be something like that but was not quite sure enough to attack the problem without a little encouragement! 40 years in the shed didn't help and the previous owner/s have done a few modifications of their own so I was not sure if I could trust the schematic! Thank for your help! Bob.

 

[Bob Johnson]

Yes I thought it would be something like that but was not quite sure enough to attack the problem without a little encouragement! 40 years in the shed didn't help and the previous owner/s have done a few modifications of their own so I was not sure if I could trust the schematic! Thank for your help! Bob.

Well Tried to start work on this, but on removing covers etc found an accumulation of dust , dirt, dead things and live things! So just dusting did nothing to remove years of neglect so the whole thing went under the garden hose!! WHAT you say???? Well T'was the only way and after an afternoon in the sun it is all dried out and still acting the same way but at least I can find the components!

 

[Bob Johnson]

OK! got started on the scope now all is dried out! (The scope shampoo and rinse didn't seem to do any harm!!) The circuit of the 529 B and A models are similar but component numbering is different so I will use the ones off your circuit diagram.
The 110V line on your diagram is labeled 175V on mine. It measures in at 185V on Q30 collector but was zero on the collector of Q29 which was running hot and although ok when tested, it was a dead short between emitter and collector with voltage applied. Pulled that out and we have 185V where it should be.( I will have to have a look at the specs of the BF337's). Next, +46 and - 47 are as they should be according to my diagram after replacing the EM404 in the +46V line.
With the X plates disconnected I get a central vertical line. By the look of nearly all the electrolytics I would say there is heaps of AC getting into the vertical amp and a lot of the resistors are way off value as well. I have sent away for some replacement parts and will carry on with something else until they get here!
Turned my attention to an FM tuner that objected strongly to having the AC power to a masthead amp applied to its' front end! More parts to wait for! But there is no shortage of things that need fixing!