Aron bs-601 scope issue

[The_Todd]

Re: Aron bs-601 scope issue

The fact that you get a waveform at all is a good sign. too bad you don't have a scope to trace the signal
Check some of the voltages on the vertical board and see if something is missing or a voltage that does'nt look right, I see a few voltages listed on the schematic so check them first

I do have a working scope

[eccerr0r]

Re: Aron bs-601 scope issue

Those voltages on the schematic are the PSU voltages and probably not enough to debug with. Not sure what else but to just trace things along since you have the other scope and have that signal generator (the probe calibration source). Else it is still possible to debug with a multimeter with the vpos pots.

I'd especially like to know what the voltages are on Q21 and Q22 as you spin the vpos pot up and down...

[The_Todd]

Re: Aron bs-601 scope issue

Those voltages on the schematic are the PSU voltages and probably not enough to debug with. Not sure what else but to just trace things along since you have the other scope and have that signal generator (the probe calibration source). Else it is still possible to debug with a multimeter with the vpos pots.

I'd especially like to know what the voltages are on Q21 and Q22 as you spin the vpos pot up and down...

I can test that, witch pins should i test on? and do you want a voltage readout or a scope signal? and witch pots to test with?

[The_Todd]

Re: Aron bs-601 scope issue

It looks like you should have -8 volts going to the center of the vert. position control, That shouuld change the bias on q29 and q30 moving the trace up or down. You say you have all the voltages but where did you check them? they may be at P3 but do they get to get to where they should. There are a number of coils in the voltage lines, make sure the voltage is on both sides of them and one is not open.

Just so i dont stuff up, witch point should i test the -8? i haveonly tested voltages at the conector

[eccerr0r]

Re: Aron bs-601 scope issue

Curious as to the voltage on the collectors of both Q21 and Q22 with just one channel on, one measurement for when the vpos for that channel fully CCW and fully CW. There should be a significant difference of the voltage at that point I would guess for the two cases, ideally they should flip flop their voltages depending on which way the vpos pot is set...

I still wonder what the voltages across D10 R80 R89 D11 D14 are. Would imagine them to be something like 12V - D10 - 17V - R80 - 90V - R89 - 108V - R89 - 114V - D11 - 115V - D14 - 120V or something like that....

*sigh* lucky people with scopes that have schematics available... I wish my 20MHz scope had schematics somewhere. Not quite the same when you have schematics for a scope that has unobtanium ICs in them like the later Tektronix...

[stj]

Re: Aron bs-601 scope issue

some tek chips have been reverse engineered.

[eccerr0r]

Re: Aron bs-601 scope issue

U800

Sigh. If the U800 blows in my 2465, I don't know if it's worth keeping the scope or just parting it. Someone has hacked up a workalike but sheesh, needs to run with stable gain at something like 100MHz or so, maybe more in 10x mode.

[R_J]

Re: Aron bs-601 scope issue

Just so i dont stuff up, witch point should i test the -8? i haveonly tested voltages at the conector

Is the vertical board easy to access? if it is You can check for the -8 volts on L4, It is located next to P1, You should also be able to check the voltage on P1, Pin 2 should be -8v and pins 1 & 3 will vary when you turn the vertical position control on the front panel for channel A
If you can, check the voltage on D10, (J5) then R80. also D11 and D14 they are near P2

[stj]

Re: Aron bs-601 scope issue

does this scope use sockets on the transistors??

[redwire]

Re: Aron bs-601 scope issue

OP fixed it, open R80 43k.

[R_J]

Re: Aron bs-601 scope issue

Good to here he has it repaired.

FROM https://www.eevblog.com/forum/repair...-amp-issue/25/
EUREKA!!!! Found the problem!!! R80 was an open line! replaced with 43k and well, now we have full range on vertical

[eccerr0r]

Re: Aron bs-601 scope issue

Dang, I told him to check the voltage across that voltage divider through R80 in post #8 ... oh well, at least it's fixed now.