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

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: 1 Guest(s)
[-]
Recent Posts
PT 6 chassis screws size???
Hello bridKarl, that sounds right or maybe 8/32 . Sincerely Richardradiorich — 01:00 AM
PT 6 chassis screws size???
Have this done except for missing chassis screws. It looks like 1 inch 6/32 sheet metal screw may work but can anyone s...bridkarl — 10:32 PM
Philco model 38 code 121 not receiving signal.
Hello Stormlord, Well done on rewinding that coil it turned fairly good for your first one. Sincerely Richardradiorich — 09:12 PM
Philco model 38 code 121 not receiving signal.
Well here it is. It ain't pretty, but hopefully it'll work. I checked it with my DMM on continuity and it keeps and r...Stormlord5500 — 08:56 PM
Philco 42-345 Restoration/Repair
Yes, 57 is an electrolytic cap that should be 12 mfd 400 volts according to the parts list from the Phorum library schem...RodB — 06:01 PM
Philco 42-345 Restoration/Repair
Looks like if I am reading it correctly it looks like the silver capacitor#57 that appears to be a replacement is of a l...osanders0311 — 05:09 PM
Philco model 38 code 121 not receiving signal.
Thanks Arran. Yeah this plastic is pretty thin. It's a little thinner than the original stuff. It kinda reminds me of p...Stormlord5500 — 04:37 PM
Testing a speaker and output transformer Trutone A2-G
The equivalent of one short turn is basically the same as that of a shorted load. If it is the primary's turn, then the ...morzh — 03:53 PM
Testing a speaker and output transformer Trutone A2-G
I've never had an output transformer become shorted, the failure mode is usually an open primary, or in a center tapped ...Arran — 03:52 PM
Philco model 38 code 121 not receiving signal.
As long as the plastic sheeting isn't too thick, I think that the thickness of photographic film would be just about rig...Arran — 03:19 PM

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

>