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

Help with the volume control - model 70
#1

I recently had to replace the dual control on my model 70 with a single control and am experiencing a strange problem.

Starting from fully off, the volume increases as I turn the knob clockwise but, at a fairly low level, the volume decreases and completely disappears as I continue turning the knob clockwise!

I don't have a scanner to show the circuit which came with the replacement kit which I purchased but I replaced the 225 ohm section of the original dual control with a 220 ohm fixed resistor and, to quote the instructions a 270 ohm resistor is added to "supply initial bias on RF and 1st IF grids".

This problem wasn't present before the change and wonder if anyone on the forum might have an idea as to what is causing this problem.

My apologies for such a long question for my first posting!

Thank you for your help.

Joseph


Messages In This Thread
Help with the volume control - model 70 - by doverite - 07-21-2013, 09:32 AM



Users browsing this thread:
[-]
Recent Posts
Correct model 84 Ac plug an cord type
From what I read Philco went to using brown rubber power cords in 1936, so cloth was used in the 1935 and earlier models...Arran — 11:25 PM
Correct model 84 Ac plug an cord type
Hi Bruce, I have not worked on an 84, but in general, power cords for almost any radio prior to 1938 was cloth covered...MrFixr55 — 08:34 PM
Restoring Philco 38-14
OK, well, so after staring at the sch again, I realized the problem had to be the #12/12A padder. I put a scope on the o...morzh — 08:15 PM
Correct model 84 Ac plug an cord type
Hello Bruce, I mostly use brown far as my cloth powercords go ! Here is the plug that I have used bakelite Acorn style...radiorich — 08:05 PM
Correct model 84 Ac plug an cord type
Looking for as correct as can find the right Ac plug an the correct colored cloth line. Ive seen many old photos but mos...Bruce — 04:13 PM
Restoring Philco 38-14
Rod Two Y-caps make sense if you use them from L/N to the chassis; this is only makes sense in the transformer radios...morzh — 10:11 AM
Restoring Philco 38-14
Mike, I'm curious about a specific use of he Y cap. Lately I've seen a single cap across the power transformer primary. ...RodB — 09:01 AM
Restoring Philco 38-14
hello morzh , That sounds like a plan ! Sincerely Richardradiorich — 07:45 AM
Restoring Philco 38-14
Richard, It helped some, but I still had the whining when engaging the rear power strip (I did not realize it was fro...morzh — 07:07 AM
Restoring Philco 38-14
Hello morzh, Yes , that dreaded hum in my room where i do alighment I have my cable modem and router plus desktop plus ...radiorich — 11:25 PM

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

>