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

model 42-322 audio distortion
#1

now that the restoration is complete with all caps replaced and deteriorated wiring redone, followed by a complete alignment, it receives stations on bcst and sw just fine. all tubes test good.

now the problem is the hum that was there before the restoration is even worse. on strong stations it doesnt just hum but it gurgles. the stronger the stations the worse it is.

would it help if I paralleled the filter caps with a higher value? also, would it help if I tied the negative side of the filter caps to the chassis instead of the end of the filament string? oh, I also found out you cannot tie the chassis to ac ground. it quickly blew the fuse I put in the ac line.

guess I need a refresher course in ac/dc radio theory and a good book on troubleshooting and modifications would sure help, along with a copy of the technical bulletins.
regards, Dick
#2

Lotsa guys here going to have better advice than me, so I'll just say it's probably not anything to do with your power supply filters. Does it get worse when you tune in a strong station regardless of volume level or anytime the volume increases? Trying to get an idea if it's in the audio section or the rf/if/det string. Did it do it with the alignment signal?
#3

kf4ns, Hi, don't parallel the electrolytics, you will put a strain on the rectifier. The electrolytics should not be grounded to the chassis they should be isolated from it bu sleeves or isolated mounting plates. I think you have a shorted cap somewhere since, depending on the size of the fuse, grounding the chassis should not cause a short. PL
#4

Well guys, I found the trouble. It is one of my most embarrassing moments. For someone with my experience and qualifications in electronics I should be tarred and feathered.

I had added a single terminal of a terminal strip just to have a place for the ICL (inrush current limiter) and used a very strong glue called shoe goo to hold it to the chassis. I failed to notice that the rivit in the back was touching the chassis. I HAD TO HOT LEAD OF THE AC GROUNDED TO THE CHASSIS. What a dumb mistake!

With it now ungrounded the radio plays BEAUTIFUL and really pulls in the stations with remarkable clarity. NOW the project is done.

Thanks to all for the support. This was a very interesting project. My first excursion into the relics of the early 40's.
Best Regards,
Dick KF4NS




Users browsing this thread: 2 Guest(s)
[-]
Recent Posts
American Bosch Model 802 auto radio
Hello again;   I found a model 838 car radio on Nostalgia Air under United American Bosch, http://www.nostalgiaair.org/...Arran — 09:32 PM
New Philco Repair Bench
Morzh is correct. The repair bench on our website is an archived image of chuck’s original site. He no longer provides s...klondike98 — 05:32 PM
Made mistake & did not label connection
Excellent information. It is all starting to come together now and your explanation really helped since I noticed that ...georgetownjohn — 04:39 PM
Made mistake & did not label connection
Hi John, I don't have this radio, but I can supply some info: Based on your pic, pins 7,8 and 1 are used together, go...MrFixr55 — 02:02 PM
New Philco Repair Bench
As far as I know, the Repairbench does not work, and has not been working in a while. Chuck (we had that campaign looki...morzh — 01:33 PM
Radio city products 664 schematic request
Need a schematic or manual for the 664. The 663 may be similar.daveone23 — 12:38 PM
New Philco Repair Bench
Thanks Gary.dconant — 12:16 PM
New Philco Repair Bench
I tried accessing the site through our library and got the same response. It's reported to our tech gurus. GaryGarySP — 11:50 AM
New Philco Repair Bench
I am sure this is the archive, and not the Chuck's site.morzh — 09:50 PM
Made mistake & did not label connection
It's not like we are good friends with that wire and can tell it from other ptetty identical looking wires. Why'n't you...morzh — 09:49 PM

[-]
Who's Online
There are currently 4269 online users. [Complete List]
» 1 Member(s) | 4268 Guest(s)
Avatar

>