Question on Emerson 611

[Rich12]

Hi everyone over the summer I worked on a couple craigslist finds. Restored an echo 425 oscilloscope and finishing up a Hoffman T1919, as soon as I figure out the vertical issue. So getting to my question, after slow progress, it was in really bad shape, I'm starting the power up tests on my Emerson 611. I've pulled the HV rectifier tube, all tubes are lighting up until 92 volts when the isolation transformer trips? I've been checking soldering, wires , etc. but no luck yet. I wanted to see if anyone has some suggestions as to a likely place to look? Thanks!

[old_coot88]

Try pulling the LV rectifier (e.g. 5U4, 5V4) and see if it still trips.

[Rich12]

I did what you suggested, thank you!! I pulled the 5V4G and it got me to 117 volts before it tripped. I then pulled the big 6BG6 Horizontal out put tube in the HV box. Same result tripped at 117 volts, but you are definitely on to some thing.

[mrjukebox160]

Sounds like a bad power transformer or a leaky X or Y cap if it has them.

[Rich12]

I'm also hearing a hum in the variac as I increase power, not too loud but it's there. I've not heard that before on anything else?

[Rich12]

Hmmm I've recapped all the old paper and electrolytics

[dieseljeep]

Originally Posted by Rich12

I did what you suggested, thank you!! I pulled the 5V4G and it got me to 117 volts before it tripped. I then pulled the big 6BG6 Horizontal out put tube in the HV box. Same result tripped at 117 volts, but you are definitely on to some thing.

That's the model with the crazy dual power supply. If it has the 5 25Z6's
pull all 5, if it has the selenium rectifiers, pull the ballast tube.
The power supply needs a total restoration before trying it again. Those things are real dogs for restoration.

[Zenith26kc20]

Without the LV rectifier tube the power transformer only provides filament. How much of a load can your variac handle? Does it have a ammeter? Mine is a 4 ampere and it works fine except on very large power amplifiers. Does the power transformer get warm at around 60 volts on the variac quickly?
You can pull all of the other tubes and try bringing it up like that. If the transformer gets hot or the variac trips, try checking voltage out from the transformer to make sure no shorts, like a ceramic bypass cap is shorted. Usually a ceramic will smoke if shorted when there are no other tubes in the circuit. Hopefully the transformer is not shorted.
The 25Z6 tubes usually die nearly instantly if there is a short. Like said, this set is a fun (read, a bit of a job!) project!

[Rich12]

thanks everyone no it doesn't have the 5 25Z6's, but it does have a ballast tube and I had to make one out of resistors, it ohms out ok on the pins. Tomorrow night I'll pull it and try powering up, good advice. The variac seems fine it does not get warm and the transformer is not warm. The 10 ohm resistors on the ballast tube heat up, but I believe thats normal.







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[dieseljeep]

Originally Posted by Rich12

thanks everyone no it doesn't have the 5 25Z6's, but it does have a ballast tube and I had to make one out of resistors, it ohms out ok on the pins. Tomorrow night I'll pull it and try powering up, good advice. The variac seems fine it does not get warm and the transformer is not warm. The 10 ohm resistors on the ballast tube heat up, but I believe thats normal.







i

I looked over the Sams and it shows the selenium rectifier version is drawn properly, where the 25Z6 version is incorrect, regarding the polarity of the 'lytics in the negative power supply.
I know your set has the seleniums, but it's easy to make mistakes in such a strange circuit. Most technicians could easily do it. Make sure the silicon diodes and the many electrolytic caps are installed with the proper polarity.
BTW, that was the first set my parents bought. The only thing that went wrong with it, was a power supply fault.

[Rich12]

Thanks Diesel, Yes the polarity on the lytics had me all confused. I'm fairly new to this, picked a helluva set to start on Lol! I had posted some pics for the group a couple months ago with a polarity question. I originally had the negative to positive, etc. P.S. I did pull the ballast tube, or I should say my home made one. The tubes lit up to 117 volts without tripping the isolation transformer. I'm going to work my way through the power supply next. I've got a new HV ceramic cap for the box to replace, etc. plus I want to work through more resistors.