Telequipment Serviscope D52 clicking noise

[pentoad]

I switched on my Telequipment Serviscope D52 yesterday and noticed it made a regular clicking noise. I haven't used it for very many years and I don't recall it doing that. Is it supposed to do that ? I'm thinking that the mains transformer is arcing.
It's not working that great as the the Y height is not 5cm on the calibration test, only half that height with DC balance fully up. Everytime it clicks the display pulses. I'm wondering if its had it
I changed a 1K cracked resistor on the TB supply - made little difference.

[WME_bill]

Telequipment D52.
Sounds like EHT flashover.Hsave you had a look with the covers off in the dark. Probably gone too high, hence the reduced scan.
I suggest check all the voltages.
wme_bill

[MotorBikeLes]

As already said, clicking probably EHT flashover. However, as it is mains derived, it is more likely to be found low rather than high. Have you stored it damp? If so, allow it to thoroughly dry out before switching on again.
Of course if your mains voltage selector is set on a too low setting ---.
It must be 35 years since I played in one of these, so very rusty. Another model with a good circuit description, so read carefully when looking for low gain fault. you don't use "DC Bal" for gain adjustment. I think the gain preset is the slotted end of a pot visible on front panel. Front end valves can go low, but you may swop with another elsewhere if it is a triode/pentode type.
Les.

[Diabolical Artificer]

Try putting it somewhere warm with the covers off after verifying it's EHT flash over. Check the EHT caps and If that doesn't stop it rounding off any pointy bits where it's arching, painting with a few coats of nail varnish or using thick plastic tape to insulate the chassis.

Andy.

[pentoad]

Originally Posted by MotorBikeLes

As already said, clicking probably EHT flashover. However, as it is mains derived, it is more likely to be found low rather than high. Have you stored it damp? If so, allow it to thoroughly dry out before switching on again.
Of course if your mains voltage selector is set on a too low setting ---.
It must be 35 years since I played in one of these, so very rusty. Another model with a good circuit description, so read carefully when looking for low gain fault. you don't use "DC Bal" for gain adjustment. I think the gain preset is the slotted end of a pot visible on front panel. Front end valves can go low, but you may swop with another elsewhere if it is a triode/pentode type.
Les.

Sorry my mistake, it was the " SET GAIN " which I used for Y height adjustment
Where do you find the circuit description / fault finding ? I have the user manual and diagrams but no fault finding hints.
Thanks

[MotorBikeLes]

All the TQ manuals have circuit description, but never a fault finding guide. I think you were expected to know how to fault find if you were repairing a scope.
My pal was into Radio and TV all his working life. He had a TQ S54, but when it had a fault, he sent it back to TQ for repair. Apparently on its way back, it got knocked, and killed the CRT.
Les.

[Pinörkel]

Originally Posted by pentoad

Where do you find the circuit description / fault finding ? I have the user manual and diagrams but no fault finding hints.
Thanks

I think back then there was a certain set of expected service technician knowledge that could be applied to most oscilloscopes. A good guide for the basics can be found in Troubleshooting your oscilloscope from Tektronix. However oscilloscopes contain dangerous voltages. However, always put safety first and only do things that you are 100% sure you know the dangers involved, and only do them if you are 100% sure you know precisely what you are doing and that you can do it safely.

[Diabolical Artificer]

Pretty sure my 52 manual has a circuit description - see attached.

Andy.

[pentoad]

Originally Posted by Diabolical Artificer

Try putting it somewhere warm with the covers off after verifying it's EHT flash over. Check the EHT caps and If that doesn't stop it rounding off any pointy bits where it's arching, painting with a few coats of nail varnish or using thick plastic tape to insulate the chassis.

Andy.

I didn't see any flashing anywhere whilst observing the internals in the dark but it was difficult to see as there was illumination from the filaments.

[MotorBikeLes]

If you look at the "filament end", you may spot CRT gun faults, but the flashovers that have been referred to here would be at the other end of the CRT, around the PDA (EHT) connector.
Les.

[pentoad]

Originally Posted by MotorBikeLes

If you look at the "filament end", you may spot CRT gun faults, but the flashovers that have been referred to here would be at the other end of the CRT, around the PDA (EHT) connector.
Les.

The clicking noise is at the opposite end at the back somewhere in the vicinity of the mains transformer or thereabouts

[pentoad]

SOLVED: clicking noise, replaced faulty c409 0.05mfd cap

[pentoad]

Is the low Y gain fault which affects both Y1 and Y2 the same, confined to the Y amplifier board?
The voltages at the b9a plug are right (although the HT's are 19vdc higher than stated in the manual)
All the valves tested good on both the amplifier board and the main board

[pentoad]

I built a test rig to test the e88ccs' for mutual conductance, they all tested mostly well under 9mA/V with 6.75mA/V the lowest.
I don't know how tolerant this circuit is to tired valves but as Y gain is an issue, I'm wondering if the first one is replaced on each channel by a new one , that would do the trick in raising the Y gain to the correct level.
I would like to get this scope working as it should do but it's probably not worth spending too much on it