[AMRadio] Type 83 in TV7 replacement

[Geoff/W5OMR]

On 6/2/2020 6:18 PM, CL in NC via AMRadio wrote:
> Does anybody have info on replacing the 83 in a TV7 with diodes?  What size dropping resistor is needed to maintain calibration?  Is there another tube rectifier that will do the job?

I found this on-line in a quick search for a type 83 rectifier... 
pretty good info.  Hope it helps.
73 de Geoff/W5OMR

Some of my experiences with Hickok tube testers, 83 rectifiers and solid 
state replacements: years ago I made a solid state replacement for the 
83 tube to mainly cut down on the heat in a WWII vintage Navy Hickok 
550X that I had bought years before from Paul Giganti. I used to run it 
for hours testing boxes of tubes and the power transformer would get 
quite hot. Well, looking at the Hickok 550X schematic and the balanced 
filament circuit I decided to try using 1N4007 type 1000PIV diodes. I 
ran one diode from pin 2 to pin 1 and the other from pin 3 to pin 4. 
Cathode (banded) end of the diodes going to filament pins 1 and 4. Well, 
this worked very well for me and I used it this way for years. I checked 
numerous different types of tubes for comparison and saw no difference 
in the meter readings. Later I tried the same thing with the 5Y3 Bias 
supply rectifier and the results were not so good. The readings for the 
tube under test were way off. So I went back to using the 5Y3GT. I 
figured the reduced voltage drop of the silicon diodes caused a change 
in the grid bias to the tube under test although I did not measure or 
verify this. Well, I left behind my 550X with Don Chester K4KYV while 
stopping at his place in Woodlawn, TN on my way to Oroville, CA. 
Recently, I picked up a long disused but nice looking Hickok 540-very 
similar to the 550X less the multimeter section. On arrival, it would 
test rectifiers fine but not any kind of amplifying capable tube. A Grid 
bias check showed grid bias to be present and the grid bias R control to 
be working. So I had to open it up. With the tester on I could see the 
problem right away-the 83 tube filament was not glowing. The tube was 
bad-resoldering the filament pins didn't help. No shorts though-that was 
good. I didn't have an 83 on hand but did sub an 80 for it and that 
worked ok for tubes with low plate current draw. So I had the tester 
working to a point. The 80 did not do so well on high plate and screen 
current tubes like when I tried to test a 25L6. Not having many parts on 
hand, I ended up going to Wilsons TV repair shop here and asked for 
parts to fix a tube checker. I got some NTE156 diodes rated 1000V @ 3 
Amps. I could only get (4) diodes. I was lucky and got (1) GE 81 lamp to 
replace the incorrect 63 that came in the tester. I decided to use only 
(2) diodes in the SS replacement as I wanted to reserve the other (2) 
for another project and my calculations showed that a single 1000V diode 
in each half of the replacement should be fine as 1/2 of the plate 
winding is rated at only 170V. I wired the SS replacement as I had done 
before and it got the 540 working quite well. 73, Rod (DeWitt) N4QNX