TEK 7704 was supposed to be working, but smoked instead.

[Opcom]

Making a short story of this, I got a 7704A at an auction, and it was supposed to be working well.

When I turned it on, after 3-4 seconds a trace began as expected, then there was a snap, no trace, and my friend started yelling 'smoke smoke!!' so I hit the breaker for the test outlet, which is always a handy thing to have on the work bench.

I do not suspect the seller of dishonesty but am confused as to what happened. Anyway, I don't have the gentleman's contact info yet and want to speak with him before I start taking covers off, so I thought it would be worth it to ask if anyone has experience with the 7704A common problems.

https://w140.com/tekwiki/wiki/7704A

[W1RKW]

maybe HV flyback divider/multiplier smoked itself. I had a Leader scope do that.

[Pete, WA2CWA]

Physical movement may have caused something to short to something close by. Ya won't really know anything until you open it up and find the smoking culprit or area.

[KA3EKH]

Love to speculate on troubleshooting! The seven thousand family can be hairy, all those direct coupled amplifiers and the like. But think the entire seven thousand family shares a couple things in common. First do you have the +15/-15 volt power supplies? The same load of crap in the low voltage power supply, the DC to DC converter that chugs along at 20 kHz or so also feeds the high voltage supply so if you are missing the +15/-15 volt bus the 20 kHz supply is dead and nothing else will work. Second, do the graticule lights work? They are powered by the HV power transformerT4201. If they are working you have good drive up to T4201, the high voltage transformer. Also want to check the +150 volt bus being that’s developed by the same transformer as the high voltage. By the time the seven thousand series came out Tektronix had already learned that there was no future in building very high voltage transformers and started using sealed HV triplers just like in analog televisions set. Because of the increased beam voltage in color TV sets and high performance scopes like that you needed stupid high voltages like 20 to 25 kV and many of the old high voltage transformers were prone to failure but when HV triplers started to appear you were able to run the flyback transformers at lower voltages and that was a big improvement in reliability on both TV sets and scopes. Its antidotal but I have seen a couple of them before and never saw a failed trippler or HV transformer.
Warning!!! The primary side of the power supply is isolated from ground, an AC Hot chassis and the entire mess floats. Be careful when probing around in the primary side, use an isolation transformer.
Pure speculation but I think that’s where you will find the problem, something like a shorted bridge or faulty filter capacitors.
I still have a seventy-six hundred and if it did not take up so much bench space would love to bring that in the shop and use it again. The seven thousand family represented a real milestone in technology with the bandwidth, versatility and on-screen display but they were so dam big and heavy.

[KD1SH]

Thanks, KA3EKH, for some excellent tips on the 7000 series. I've got a 7623A that stopped working a few years ago, and haven't yet had the time to get into it. It's big and heavy, like you say, and takes up valuable space on my shelf, but I love it so much that I can't bear to get rid of it. When I finally do pull the covers off it, your info will be helpful.

[KA3EKH]

That was a great family of products, not just as scopes but you would also be able to pop in a 7L12 or13 spectrum analyzer and you would be uptown. I am starting to weaken and thinking maybe I can drag the entire mess in and use it on the scope mobile.  The problem is I have one of those Tektronix TDS scopes on the bench now that I use and its hard to beat for the cost, and think it weighs less then a tenth of the old 7603 and takes a small fraction of bench space.
Maybe one of the smart people on the list can calculate how many cubic inches of space the 7603 uses verses the TDS family of scopes?

[n8fvj]

I bought 5 AM transmitters from the 1950s & 1960s from Hams that stated were working. None worked.

[Pete, WA2CWA]

Making a short story of this, I got a 7704A at an auction, and it was supposed to be working well.

I do not suspect the seller of dishonesty but am confused as to what happened. Anyway, I don't have the gentleman's contact info yet and want to speak with him before I start taking covers off, so I thought it would be worth it to ask if anyone has experience with the 7704A common problems.

Well, it could be that the original owner did not allow any smoking at their location.
Now, new location; test the water to smoke