Tektronix 465 oscilloscope problem

[in_titusville]

I purchased a Tektronix 465 oscilloscope on ebay about 2 months ago. It worked fine for a few weeks then turned it on one day and lights but no trace. I took the cover and found a blown 1 1/2 amp fuse. I replaced the fuse and as soon as I power on the fuse blows. I assume this fuse is for the high voltage power supply since the other lights work but no display. I searched but can find any 465 repair or maintenance manuals on-line. This is a good 30 years old or more so I really don't want to put too much money in to fixing it. Anyone have these manual or link to a location with these manuals and/or schematics.?

 

[in_titusville]

OK... Did more searching and found a Tektronix 465 service manual with schematic. I will post this .PDF file shortly. Look like the fuse in question is F1419 1 1/2 amp fuse that comes off the transformer and supplies 15V unregulated power, from there it just and arrow which means you need to search the schematic pages to find the other 15v unregulated arrows. My wild guess is a cap or voltage regulator is somehow shorted somewhere down the line. This scope is built like a tank and isn't easy to take apart. I may just give in and send it to a repair shop to fix this.

 

[gootee]

You could first ask the guys on the Tekscopes group, at yahoogroups.com, what might be the most likely culprits, or how best to go about narrowing it down. Ditto for the sci.electronics.repair group at Google Groups . Both groups have people who are very knowledgable about Tektronix scope circuits and their troubleshooting and repair.

 

[HiTech]

Just find each section that uses 15 volts and lift them from that supply rail. Now measure each section's 15v input to ground. Note any abnormally low resistance readings and that leg is suspect for the failure of the fuse.

 

[ben7]

Get a multi-meter and check to see what is shorted out.

 

[kd5fpo]

possible Tek-465 solution

If you haven't checked the tantalum caps in your 465 yet, you should. Dipped tantalum caps are a principle cause of problems in older test equipment, especially anaolg 'scopes. My 465 suffered from three bad tantalums, simple replacements netted me a perfectly working 465. Best analog 'scope ever made. 73 KD5FPO

 

[tunedwolf]

The Tek-465 were possibly the most ruggedised ever built and were often used by the armed forces around the world. Tant caps do go bad in them and the odd diode. I haven't seen much in the way of other faults in them, other than the usual calibration wipers problems.

rgds

 

[kd5fpo]

Tek-465 problem

If you're not familiar with testing caps, those weak tantalums simply need to be checked for zero ohms, if they read zero on a DMM then they're shorted and need to be replaced. One lead will need to be clipped before testing to isolate it from the circuit. Yes, it's a pain, but such is life.
I replaced mine with mylar caps and they worked fine. I'd love to have a digital Tek-'scope, but the 465 is the next best thing.
73 KD5FPO

 

[dukkas]

HI, good day to all.
I recently received a SCOPE 465 from a friend, but it´s not work. iam downloaded a MANUAL and disasembled the scope.
the circuit for HV canot start. no fuse burn, transistor and diodes burned, 120, 110, +19 +15 +5 OK and the -8 no OK, only 5volts, i looking for all components and do not locate any problem.
I think have a 3 tantalum capacitors, it´s possible substitute it for any eletrolitic for test? any person have more informatios to send to me? i like to use the 465, but need it´s work fine...
I washed the case and the partys to make appereance a NEW equipament... thanks for all...