Dead Fluke 6070A signal generator opinions?

[flolic]

I can get old Fluke 6070A signal generator, not working, for around 150 to 200 euro. Seller has few of them in the same condition, and I can pick one that I like from the batch. According to him, all units are dead and have problem with the power supply not starting. Apparently, source of the problem is shorted tantalum caps on various boards.

I could really find use for such unit, but I don't know is it worth the risk?

[KJDS]

If the seller knows what the fault is, why hasn't he fixed them?

[Wim13]

The Fluke 6070 has a protection on all the power voltages, i does not startup if one of the voltages
of the power supply is wrong. I have repaired one, and was only the 24 Volt serie regulator on the
serial power board was defective. after replaced it by a TIP transistor it worked oke.

But if no luck , it can also be in the switched power block. It has a switched power supply.
Thats is quite unusual for a signal generator can give a lot ogf noise, thats why they put in an extra power serial
regulator board, just to make from 6 V => 5 V and 13 V =>12 and 25v => 24 V. etc.
When i measured the 24 Volt i got 25 volts, so you think not to bad..

[flolic]

Thank you Wim13. I think I'll try my luck with one of those units, because price seems fair.

If the seller knows what the fault is, why hasn't he fixed them?

Seller got 4 of those as part of some business deal. He is selling them "as is" and has no interest trying to fix them.

[Wim13]

Be sure all parts are there, or try to get a picture from inside.
and from behind to be sure the power supply is there.

And if it has a menory board option, there is a lithium batt on that board.
That can be empty.

[flolic]

I will meet with the seller in a 10 days, and pick up one that looks best.

[jstearns]

We designed a switched power supply for the 6070A because we wanted to fit everything into a 13.3cm high rack box with modest cooling requirements.  An analog supply would have required a large transformer and cooling fan to dissipate the heat.  That wasn't acceptable.

Switching supplies were new and rare back in 1977 when we designed that supply.  It was a completely custom design, as there weren't any off-the-shelf switched supplies back then.  I recall that the power transistors were hard to source.  The engineer who designed the supply was very aware of the noise and ripple requirements.  We were skeptical that a switching supply could meet those requirements, but his design did.

After all these years, the tantalum caps are likely to be the problem.

I imagine that you can find the schematic online.  If not, Fluke should be able to help you.  Fluke had excellent document control, so I imagine that the company still has the records for that product.

[wn1fju]

I have the 6071A which is basically the 6070A with a frequency doubler.

If you are inclined to fix things, I strongly suggest you first download and look through the (multi-volume) manual set to see if you want to take the plunge.  It is not a simple case of removing the top and/or bottom cover and gaining access to 90% of the parts, as it often is with test equipment.  The 6070/1A requires a lot of careful disassembly, especially in the front panel area (where, of course, one of the tantalums in mine recently exploded). 

Also, the calibration procedure is long and complicated and if any repairs effect certain calibration constants stored in EPROM, you are basically out of luck since Fluke says in the manual that one should return the unit to Fluke for reprogramming.

As far as the unit goes, it is an OK signal generator.  I much prefer, however, the Fluke 6080A/B or the lesser 6060A/B if you can find one of those cheap.