Posts: 933
Threads: 140
Joined: Mar 2015
City: Lansdale
State, Province, Country: PA
All, Started on this 46-350 Radio. I measured the resistor string from the 117Z3 Rectifier. R100 on diagram.
This is a Cadohm resistor on chassis. It measured high except for 1st section. .. Question is Since this for the Filament string how close does it have to be.
[Image: http://i292.photobucket.com/albums/mm38/...e5z0ys.jpg]
If its a higher resistance it would be a lower voltage which is good for 1 volt tubes but how much is too low..
I guess I cold try to replace it but what wattage would I need . Or could I just put a resistor in Parallel to get the resistance to match Then question is again what wattage resistor.. I also assume that I have to match the Caps too.
Skip...
Posts: 1,113
Threads: 14
Joined: Feb 2013
City: Irvington, NY
I would hold off on changing the resistor until you get the radio powered up. Then measure the DC voltage at the point labeled 8.5V and see what you read. Given today's higher line voltage a little more resistance might be a good thing.
The candohm dissipates somewhere around 4 Watts so you will need more than regular carbon resistors ( .05A x 80V drop).
The only critical cap value would be C100A which is the first filter after the rectifier and affects the DC output voltage. C100B, C and D can be larger for more filtering.
Posts: 933
Threads: 140
Joined: Mar 2015
City: Lansdale
State, Province, Country: PA
Thanks, I will do that..
I just didn't want to burn out any of those 1 Volt tubes. But I will bring up on a Varaic anyway and monitor that point
Skip...
Posts: 933
Threads: 140
Joined: Mar 2015
City: Lansdale
State, Province, Country: PA
Ok restarting on this radio.. Parts just arrived caps I was missing...
I just saw another post about a Cap wrapped by wire.. Here is a picture of mine.. I re-stuffed cap and left wire in place..
[Image: http://i292.photobucket.com/albums/mm38/...ugdsxo.jpg]
Here are a few more pictures of bottom Have 4 Caps to replace yet..The Electrolytic can was re-stuffed ..
[Image: http://i292.photobucket.com/albums/mm38/...jzfssx.jpg]
The 4 caps on right still need replacement..
[Image: http://i292.photobucket.com/albums/mm38/...ygjf3p.jpg]
More to Follow..
Skip...
Posts: 4,611
Threads: 51
Joined: Sep 2008
City: Sandwick, BC, CA
In answer to your question battery tubes are generally happiest at about 1.4 volts but perform poorly at anything below about 1.2 volts, especially tubes like the 1R5.
Regards
Arran
Posts: 933
Threads: 140
Joined: Mar 2015
City: Lansdale
State, Province, Country: PA
Well finished recap. Started to power up on Variac.. I get no voltage anywhere no current draw either. .. Not sure if tubes are even lighting up. My guess is I have a bad tube somewhere? But shouldn't I get some voltage with only the 117Z3 rectifier tube in? See previous schematic??
Skip...
Posts: 1,113
Threads: 14
Joined: Feb 2013
City: Irvington, NY
Is the 117Z3 lighting up? Where are you connecting the negative lead of your DVM?
The chassis of the radio is isolated from the circuit ground. Measure from the common negative of the filter caps to the cathode of the 117Z3 and see if you have any DC voltage.
Posts: 933
Threads: 140
Joined: Mar 2015
City: Lansdale
State, Province, Country: PA
OK.. negative lead to B- Positive lead to Pin 6 Should read 90 Volts.. As I bring up on variac when I get to about 90 Volts input the Current starts to rise to around 400 Ma. That sounds way to much current for this.. Its only listed at 25 Watts so Thats about 200 Ma..at 117 Volts in..
Pin 6 only reads about 9 VDC. I only ran it that way for a few seconds as the current was 400 ma..
Replaced Caps.. C100A B, C and D along with all others ..
117Z3 tests good on my tube tester..
Ps I didn't notice the other tubes lighting up but at only 1-2 volts on Filament I probably could not see them...
Ideas???
Skip...
Posts: 1,113
Threads: 14
Joined: Feb 2013
City: Irvington, NY
Seems like you have a short across the B+ supply. Is the polarity correct on all the electrolytic caps?
With the set unplugged, measure with an ohmmeter from pin 6 of the 117Z3 to common negative of the filter caps.
You should see a high and rising resistance value.
Disconnect the wire from R100A to pin 6 of the 117Z3 and power up slowly. See if the input current is still high and if you now have around 90 VDC at pin 6 with normal AC input voltage.
Posts: 933
Threads: 140
Joined: Mar 2015
City: Lansdale
State, Province, Country: PA
Ok, I will double check polarity. Yup you were right Stupid Me...
Every one of the Caps C100A, B, C and D were in backwards. When I rebuilt the Can Luckily I didn't seal it back up yet.. So its a easy fix to turn caps around..
PS Did I damage the caps and need to use new ones? Or do you think the old ones are OK..
Skip...
Posts: 7,212
Threads: 266
Joined: Dec 2009
City: Roslyn Pa
(12-26-2016, 04:20 PM)vecher Wrote: Ok, I will double check polarity. Yup you were right Stupid Me...
Every one of the Caps C100A, B, C and D were in backwards. When I rebuilt the Can Luckily I didn't seal it back up yet.. So its a easy fix to turn caps around..
PS Did I damage the caps and need to use new ones? Or do you think the old ones are OK..
Skip...
Chuck em!!!!!
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
Posts: 667
Threads: 11
Joined: Sep 2014
City: Bellmawr, NJ
I'm surprised they didn't,,,,,POP
Posts: 933
Threads: 140
Joined: Mar 2015
City: Lansdale
State, Province, Country: PA
Roger that.. New ones it is.. This time the right direction...
Skip...
Posts: 933
Threads: 140
Joined: Mar 2015
City: Lansdale
State, Province, Country: PA
Ok, Re-caped. The right way... I now get voltage.. But no sound in speaker.. I can hear some scratches when turning the volume control. So I will now hook up the loop to see if it makes any difference.. I hope so..
Skip..
Posts: 933
Threads: 140
Joined: Mar 2015
City: Lansdale
State, Province, Country: PA
Ok, Put radio back in case hooked up Loop antenna .. Works.. Good volume and many stations across the band. The volume control is scratchy.. Looks like I have to take apart and lube it.. Stations sound a little distorted . Maybe due to volume control or alignment..
But good progress made..
PS Note to Self...MUST Remember to put in Electronic Caps correctly...
Skip...
Users browsing this thread: 1 Guest(s)
|
