Welcome Guest! Be sure you know and follow the Phorum Rules before posting. Thank you and Enjoy! (January 12) x

Thread Closed
Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5

The 39-116 project: the beginning
#9

I made up a SS 80 with a couple 2.5A 1KV diodes. That brought the B+ up to around 320, that helped.

I finally have the remote receiver working with good (I think) sensitivity. I can trigger the thyratron with a -34dB input to the terminals. It will stay triggered down to -41. It was tricky to get it right, as the impedances on the grids of the 87 and the 6J7 (I'm temporarily using a 6K7) seem to be quite high, and even my scope probe loads them to a point they won't properly tune. I ended up feeding a +10dB signal in and getting the thyratron to fire, then backing the level off till it extinguished. I then tuned the first stage until it fired again then backed the level off till it extinguished again. Lather/rinse/repeat until I found what appears to be the best gain.

Now the next fun part. The stepper does not work reliably. This could be because I'm not able to send it properly spaced pulses until I get the Mystery Control working. We shall see.

The final chassis issue I have not wanted to deal with because it's going to be a total PITA is the volume control. This one has issues. Toward the lower end, it acts like a typical old volume control with either dire need of cleaning or a completely worn out trace. The volume jumps around as well as the timbre and the amount of distortion. If I find a sweet spot where the thing makes proper contact, it sounds great, but in the meantime it crackles and just makes very unpleasant noise. Once it's past this bad spot on the way up, it works fine and sounds great (but loud!!) This one of course is far more problematic to clean because it moves so slowly as you run the motorized volume up and down. I shudder at the thought of having to replace that control...


Messages In This Thread
The 39-116 project: the beginning - by BrendaAnnD - 03-20-2015, 05:47 AM
RE: The 39-116 project: the beginning - by morzh - 03-20-2015, 10:39 AM
RE: The 39-116 project: the beginning - by morzh - 03-20-2015, 02:39 PM
RE: The 39-116 project: the beginning - by BrendaAnnD - 03-22-2015, 02:48 PM
RE: The 39-116 project: the beginning - by morzh - 03-28-2015, 11:54 AM
RE: The 39-116 project: the beginning - by morzh - 03-28-2015, 12:43 PM
RE: The 39-116 project: the beginning - by morzh - 03-29-2015, 11:04 AM
RE: The 39-116 project: the beginning - by morzh - 03-29-2015, 11:37 AM
RE: The 39-116 project: the beginning - by morzh - 04-15-2015, 09:39 AM
RE: The 39-116 project: the beginning - by morzh - 04-15-2015, 09:59 AM
RE: The 39-116 project: the beginning - by morzh - 04-16-2015, 05:11 PM
RE: The 39-116 project: the beginning - by murf - 04-19-2015, 05:49 PM
RE: The 39-116 project: the beginning - by Edisla - 10-24-2017, 03:55 PM



Users browsing this thread:
[-]
Recent Posts
Philco Model 38-7: what caps & resistors do fail typically?
Since you stated earlier, you have a console 38-7XX.  They also had a 38-7T (table), and 38-7CS (chairside).  A very nic...GarySP — 01:18 PM
Part numbers to model cross
That I wouldn't know, but sometimes the radio document itself shows one, same as the capacitor cans' etc pinouts.morzh — 12:46 PM
Part numbers to model cross
Thank you morzh, that is exactly what I was looking for. Now , is there some where that shows pinouts for Philco power ...Jim Dutridge — 11:37 AM
Restoration of the Canadian General Electric A-87
Thanks for your help Michael. In fact, this video is only an intermediate result. Later I had to apply another tinting l...RadioSvit — 09:01 AM
Restoration of the Canadian General Electric A-87
Great job on the cabinet. PS. In the US notation, "kenotron" refers to specific type of tubes; we call re...morzh — 08:24 AM
Part numbers to model cross
This document has at least some tables of models and parts used. Example: Choke 32-7572, used in 604 radio. Search f...morzh — 08:19 AM
Restoration of the Canadian General Electric A-87
I also checked all the radio tubes on my Hickok 530 tube tester. The 5Z3 kenotron turned out to be faulty, all the other...RadioSvit — 08:02 AM
Restoration of the Canadian General Electric A-87
Well... While the varnish is drying up, I started repairing the chassis... Of course I started by replacing the pa...RadioSvit — 07:12 AM
Philco Model 38-7: what caps & resistors do fail typically?
Hello Martin, Welcome aboard our little community what great Model 38-7 Sincerely Richardradiorich — 12:30 AM
Philco Model 38-7: what caps & resistors do fail typically?
Welcome to the Phorum Martin. I count about 9 paper caps, the 3 electrolytic caps and 2-Y2 safety caps to replace th...RodB — 09:44 PM

[-]
Who's Online
There are currently no members online.

>