HP 1740A Help

[PigHeaded]

I have a HP1740A Oscilloscope that does not display a signal. I took the cover off and I do not have a glow in the CRT. Before I spend money on a replacement CRT I would like to know if that is the problem. There are several wires that connect to the back, the top and the side of the CRT, but I do not have a service manual to tell me what they should read. Does anyone here know? I will be getting a service manual, but I wanted to order a CRT at the same time, if it is the problem.

Thanks,

Sean

 

[Nigel Goodwin]

I have a HP1740A Oscilloscope that does not display a signal. I took the cover off and I do not have a glow in the CRT. Before I spend money on a replacement CRT I would like to know if that is the problem. There are several wires that connect to the back, the top and the side of the CRT, but I do not have a service manual to tell me what they should read. Does anyone here know? I will be getting a service manual, but I wanted to order a CRT at the same time, if it is the problem.

I would have thought it's EXTREMELY unlikely to be the CRT, more likely the power supply is faulty!. It's a very trival job to check the CRT for such a potential fault - it can only be caused by the CRT heater being O/C - which you can test with an ohm-meter.

I also expect you would be astonished at how expensive a replacement CRT would be!.

 

[PigHeaded]

Thanks for the quick response. Do you know which lines are for the heater? I have not been able to find a pin layout for the CRT online.

Thanks,

Sean

 

[Nigel Goodwin]

Thanks for the quick response. Do you know which lines are for the heater? I have not been able to find a pin layout for the CRT online.

Sorry, but I've no idea - but it should be fairly easy to work it out, for a start they will be the only two that read a low resistance.

 

[PigHeaded]

Thanks again. I Will run through the pins.

Sean

 

[ljcox]

I have a 1740A and a Service Manual. But I am not at home at the moment.

In what country do you reside?

 

[PigHeaded]

Hello ljcox,

I live in the united states. I would love to get a copy of the service manual!

Also note that I checked out the pins and found that the heater is receiving 6.3 volts. I than pulled the connector off the crt and found that the heater pins are open. So the crt is bad. Now I have to find a cheap crt. Thanks for helping me find this information out.

Sean

 

[ljcox]

Sean,
I sent you a PM yesterday, did you receive it?

 

[zevon8]

other than buying a part donor scope, here is one option:

https://www.sphere.bc.ca/test/hp-crts.html

The CRT ( # 5083-3552 ) for your scope is $120 factory new, or $80 fpr a used pull.