Posts: 403
Threads: 40
Joined: Feb 2011
City: McPherson, KS
Hi guys,
Been working on this nice little cathedral. I've changed the filter caps (but not the caps in the blocks), a couple of resistors, and have it powering up. All I'm getting is a soft hum now. I have a suspicion the oscillator coil isn't working. However, I'm wondering about the caps in the blocks. What do you guys think....caps or coil...or something els?. What's a good test on the osc. coil? Tubes test strong.
Thanks,
Art
Posts: 7,301
Threads: 269
Joined: Dec 2009
City: Roslyn Pa
(03-23-2012, 11:04 PM)Art Hoch Wrote: Hi guys,
Been working on this nice little cathedral. I've changed the filter caps (but not the caps in the blocks), a couple of resistors, and have it powering up. All I'm getting is a soft hum now. I have a suspicion the oscillator coil isn't working. However, I'm wondering about the caps in the blocks. What do you guys think....caps or coil...or something els?. What's a good test on the osc. coil? Tubes test strong.
Got to do it all and the resistors.
Terry
Posts: 201
Threads: 26
Joined: Dec 2005
City: Morris Plains, NJ
Do you or any friends have a scope? With it you can quickly see if the oscillator is working.
It's very important to measure the plate and screen voltages before you do anything.
Pete
Pete AI2V
Posts: 403
Threads: 40
Joined: Feb 2011
City: McPherson, KS
Do you or any friends have a scope? With it you can quickly see if the oscillator is working.
It's very important to measure the plate and screen voltages before you do anything.
Pete
*********************
No, no scope.
I have already removed two (not simultaneously) of the capacitor blocks filled with tar and am soldering back the connections on the second one (7625SU). Kind of messy because even though I have read how to the the tar out "easily," ( http://www.philcorepairbench.com/capbuild.htm), (step 4--fig.4) is not working for me, and I have had to melt the tar to empty the block.
Along the way, I found resistor 22 listed in the parts list with a value of 24K but in the schematic it is 240K. And to beat that, the resistor in the radio actually was a 420K which tested @ 393K. So I have a conundrum: which should it be????????????????
Art
Posts: 2,128
Threads: 18
Joined: Oct 2008
City: Merrick, Long Island, NY
Do you or any friends have a scope? With it you can quickly see if the oscillator is working.
It's very important to measure the plate and screen voltages before you do anything.
Pete
*********************
No, no scope.
I have already removed two (not simultaneously) of the capacitor blocks filled with tar and am soldering back the connections on the second one (7625SU). Kind of messy because even though I have read how to the the tar out "easily," ( http://www.philcorepairbench.com/capbuild.htm), (step 4--fig.4) is not working for me, and I have had to melt the tar to empty the block.
Along the way, I found resistor 22 listed in the parts list with a value of 24K but in the schematic it is 240K. And to beat that, the resistor in the radio actually was a 420K which tested @ 393K. So I have a conundrum: which should it be????????????????
Art
[/quote]
Please post schematic or post to schematic. Probably you can answer your own question.
Posts: 411
Threads: 42
Joined: Sep 2008
City: Ironton Ohio
It may have been another production run or code than that of the schematic you have, they changed many things as a radio was produced as to repair issues that would come up.
Posts: 403
Threads: 40
Joined: Feb 2011
City: McPherson, KS
(03-27-2012, 11:31 PM)tab10672 Wrote: It may have been another production run or code than that of the schematic you have, they changed many things as a radio was produced as to repair issues that would come up. ****************
True. I'm going with a 240K resistor.
Posts: 403
Threads: 40
Joined: Feb 2011
City: McPherson, KS
Radio has all new caps and resistors replaced if out-of-tolerance. However, radio not playing yet ---- and a wire-wound 325 ohm resistor (#30 on schem) connected to transformer gets VERY hot. Is this a sign of a bad transformer?
Posts: 7,301
Threads: 269
Joined: Dec 2009
City: Roslyn Pa
No I don't think so. Check the polarity of the filter caps. Sounds like you've got one in backwards. How much juice you got from the chassis to the filament of the 80 tube?
Terry
Posts: 403
Threads: 40
Joined: Feb 2011
City: McPherson, KS
Thanks to Terry's help with the oscillator coil, this little cathedral is playing like a champ w/lots of bass from the speaker.
It's missing the little lug tap on the sensitiviy control on the back of the chassis. Does anyone have a spare they could send me? Right now I have it "bushed" up and held with a very small tap but suspect it might be losing some reception from that rigging.
Thanks in advance if you can help.
Art
Posts: 403
Threads: 40
Joined: Feb 2011
City: McPherson, KS
It's missing the little lug tap on the sensitiviy control on the back of the chassis. Does anyone have a spare they could send me? Right now I have it "bushed" up and held with a very small tap but suspect it might be losing some reception from that rigging.
****************************
Thanks to Terry (again) for supplying the lug tap. I appreciate you very much.
Art
Users browsing this thread: 1 Guest(s)
|
Recent Posts
|
My collection presentation
|
There is an article on my site that introduces the first portable radios in my collection. I have only provided a link t...Vlad95 — 01:17 PM |
Electrolytic restuffing/internals
|
Bridkarl
This specific cap you have is the easiset type to restuff.
I usually cut it at the upper border of the depr...morzh — 11:35 AM |
philco predicta
|
Hi CGL18,
First off, welcome to the Philco Phorum. I have not worked on a TV for a while but here are some givens:
...MrFixr55 — 08:22 AM |
Another amp build - here I go again!
|
Sweet!
I actually have a Dynaco Mark 4 that I had been running with 6L6s with no mods. Seemed to my 14-year-old head a...MrFixr55 — 12:57 AM |
PT-6 finished!!
|
Hi Gang,
Tube heaters are not "Ohmic" devices (that maintain specified resistance over wide temperature, c...MrFixr55 — 12:03 AM |
Electrolytic restuffing/internals
|
Look here:
Philco-F676-124
Vlad95 — 08:02 PM |
PT-6 finished!!
|
Well the 35Z3 doesn't have a tap on the tube heater for a pilot light, so in this set they have the dial lamp paralleled...Arran — 06:21 PM |
Electrolytic restuffing/internals
|
Thanks. I think I try to cut this as suggested. I don’t have a lathe, but I do have a tap and die set. I am going to see...bridkarl — 04:46 PM |
Another amp build - here I go again!
|
Hey all! Well, I guess that with what I learned from my last build, it's time to move up the ladder another rung and tak...TV MAN — 04:38 PM |
Electrolytic restuffing/internals
|
There are various ways to handle this, one is to cut near just above that rolled in area is near the bottom, using the r...Arran — 04:36 PM |
Who's Online
|
There are currently 1178 online users. [Complete List] » 1 Member(s) | 1177 Guest(s)
|
|
|

|