Spent a good part of yesterday melting tar (rebuilding bakelite caps) and measuring resistors. Didn't find many that where within the 20% tolerance. A couple of the paper tubular caps rather than restuffing them they got a layer of Scotch #33. Don't really like the yellow look. For #93 & 94 (plate bypass for the 42 output tubes, .006 @ 1000v) used a couple of .01's in series = .005 @ 1260v. Those I slipped the old cardboard tube over. Have two or three more bakelites to do over in the detector/avc circuit.
Was thinking about the shadowmeter, I have a spool of 44ga wire and was thinking that might be easier to get up to the proper resistance. Not sure if that is the goal or it's the more turns the more magnetism? Also not sure how much current I can pass though #44 wire I'm thinking that 10-15ma would be good. Of course this may be academic cause #44 maybe too difficult the wind.
O btw the cap order came in yesterday.
Terry
(This post was last modified: 06-24-2016, 12:36 PM by Radioroslyn.)
Maybe tonight or tomorrow. I'm getting a little low on breakfast food so will be making some waffles to freeze tonight. Hmmmm waffles and tar..... For now not too worried with the shadow meter. Have one extra cap that I'm not quite sure where it goes but will figure it out.
Powered it up late last night and found that off/on switch isn't working, was kinda stiff before so will have to give it a good cleaning. Hot wired it and got power. Power supply is working fine but radio has some issues. Volume is low and no reception just background noise. Fed a 460kc signal down the IF and seem to be working. The LO I'm not so sure as I'm getting several oscillation and it doesn't seem to be mixing. Did use the generator for the LO and was able to tune in some stations but where nowhere near where they should be on the dial.
Going to focus in on the audio/det stages to see what is causing the low audio and the osc/mixer. Maybe an out of alignment issues but most of the time I'm not that lucky!
Terry
(This post was last modified: 06-25-2016, 08:51 AM by Radioroslyn.)
<is a big positive.>
Yes it is, about 300v.
I didn't mention last night I had a little fireworks. 91 the dual mains bypass cap blew it's top BANG!!!!! So that was exciting. I haven't done an ortopsy but I think I may have over heated one of the leads inside the bakelite block when soldering on the outside connections. One of the leads may have been touching the outside of the other cap and with some heat added it could melt the yellow mylar and shorted to the foil innards.
After poking around a bit I found that the plate voltage on the mixer and 1st IF was low like 80vdc, should be 200vdc. Did a little investigation to find that I had done a little miscalculation. #47 is in parallel with the shadowmeter coil and is 2000 ohms. I replaced it with a 2300 ohm resistor. At first thought I was thinking that 47 was used to set the amount of current thought the shadowmeter's coil. Make it higher and you'll get more deflection lower and you'll get less deflection. But upon looking a bit closer it also controls the plate voltage for the mixer/IF amp. With a good coil and resistor you should have about 800 ohms. My coil is open. I had 2300 ohms. Replaced it with a 750 ohm resistor (had it on hand) and did some voltage check, things looked a lot better.
Flipped it back over and realigned the IF stages. Before didn't have much gain, had to crank up the output of the generator to get a signal and the adjustment didn't peak very well was really broad. With the right voltages the peak is much more pronounced and have the generator output all most all the way down. All this is good!
Had pulled the 76 tube out while I was troubleshooting put it back in and hooked my 25ft test ant (cord for the Eletrolux sweeper) and we got stations!!!. Volume is still a bit low and volume control is dirty so it's next on the list for cleaning.
Terry
(This post was last modified: 12-02-2016, 07:28 AM by Radioroslyn.)
The bakelite block inside was ok no shorts but the outside, one of the terminals was burn off. Thinking it was some solder splatter or something. Put it back together is work fine. Cleaned the volume control and lubed the switch. reinstall and works good now.
But have a couple of other issues. Screen voltage on the rf/mixer tube is low about 45v should be 80v. The dial cord for the dial mask broke and audio has some hum. Pretty sure it's coming from the det/1st audio stage.
Restrung the cord for the arrow mask and started in on the SG voltage problem. After half a day of troubleshooting I found that I had installed a wrong value resistor. Now the screen buss is up to 75v. Hum was found to be a bad resistor over in the tone circuit. Also had an intermittent, volume would change all by it self. Was a bad connection at the ant post. Disassembled the spkr plug someone in the past did a bad job repairing the wiring. Cleaned it up evened up the wires and add some heat shrink tubing to give it a bit of strength. I was playing with it a bit and changed the value of #14 and it improved the high frequency response of the audio. Sound really good!
It's been playing for about 8hrs with out a problem. If I could only get that 42-854 to do the same!!! Waiting on a few small parts bulbs and such. Also want to do the SW/LW alignment BC and IF are good.
Currently It's playing Information Please, I always feel smarter after listening to it!
Stand back! My head is going to explode!!!!!
Turned this set on and got a low hum and after 15sec the 80 tube's plates are starting to turn RED, their not suppose to. Quick turned it off and hooked up the voltmeter to the hv. Should be about 350v was 125v, that's why the 80 was getting an angry red. Personally I like a dead short there much easier find. Ones that have a few thousand ohms across the hv are a bit trickier to locate. Started to disconnect some of the resistors feed the hv to various stages, It's not there. Ungrounded the filter caps and bypass cap, their ok. Next I started unplugging tube all but the 80. Magically the hv jumped up to 350v.Hmmmm.. Reinserting the tube one by I got the last one, one of the 42 output tubes. It sucked the voltage down to 125v again. Replaced the 42 and all is well I though.
I wanted to go though the rf alignment to make sure it's working on all band and such. The BC band was in good alignment. Checked over the police band. Philco sez to set the upper end of the band at 4.5mc (there is no marker at 4.5mc however there is one at 4.6mc) a little odd but I can count. Did the LW and SW bands. Now the trimmer to adjust these are not laid out very logically so I may have tweaked one that I had already adjusted. Anyway went back to the bc band and now at 1700kc I'm picking up a local at 1210kc. Low end is good 600kc is still at 600. The upper end is only tuning up to 1210kc = lo is operating from 1010kc to 1670kc. It should be working up to 2160kc. Somewhere I lost 490kc. After checking connections,bandswitch, trimmer cap and coil. I'm coming to the conclusion that the coil is bad but two things bother my about the coil prognoses. Darn thing oscillates and it has a low resistance (about a quarter what the diagram shows (1ohm verses 4.2) The high end trimmer (29) has very little effect on the frequency about 1kc or less throughout it's range.
As you can see from the diagram the osc coil doesn't have a feedback winding it uses caps to couple the signal from the plate to the grid. So it's just a single winding with a tap for the low end padder. I suppose I could make a prototype to get the right amount of inductance and the tap in the proper place. The old one has a bunch of wires going to the bandswitch real a pita to get apart. Also thought about using a replacement bcb osc coil but not sure if I can get the proper range out of it.
Any thoughts??
Terry
(This post was last modified: 07-03-2016, 11:39 PM by Radioroslyn.)
So I haven't given up on it but a few things have happened since last posted. Started to homebrew a replacement osc coil for the bc band. Did get to oscillate but need to remove some turns as it oscillates too low in frequency. Started with about 110t of 36g wire tapped at 10t for the padder.
Meanwhile I was digging though some loose parts on my workbench in the basement and found a Miller OSC-69 coil. It's a universal replacement coil so I may give it a go to see if it will work in this circuit. It's alot smaller than the one I wound up and would be easier to mount.
The red plate in the rectifier has reared it's ugly head again which is starting to annoy me a lot. B+ was down to 150v or so. This is getting tiring really tiring! But it wasn't the 42 tube it was the tube socket that I replaced, it was arcing though the thin wafer up to the chassis. Found 20 replacement molded sockets for a buck a piece. Should be here by the end of the week. I may do some more work with the coils and just leave the socket disconnected till the replacements get here.
The top coil is the homebrew coil. To put them into perspective it's a 1/2" in diameter the Miller coil is a 1/4"
(This post was last modified: 07-03-2016, 09:08 PM by Radioroslyn.)
The sockets came in today and now I have a life time supply of six pinners. Some came with the metal mounting bracket and other with just the snap ring. If I'm really lucky the hole in the chassis with be just the right size that I can mount with just the snap ring, but I'm not holding my breath!
I guess I have no excuse now not to work on it. I found a capacitance calculator on line and determined that my quick calculation of 182 mmfd was way off. It should be closer to 500 mmfd. I'm glad I found this out else I'd be doing the trial and error thing a lot longer.
I was right the hole was too small to fit the socket from the top so I enlarged the hole about 1/32" and was able to get it in. But now the issue is that the chassis thickness makes in darn near impossible to fit the retaining washer in place. So now I'll have the enlarge the hole a bit more so I can fit it from the bottom with the mounting bracket underneath. Removed the other 42 socket too so I won't have an arcing problem from the other socket.
Hey Ron tell Deb that I just finished the last brown sugar/cinnamon cookies , they stood the test time! Found a few after digging though some of the stuff that I came back with.
Terry
(This post was last modified: 07-07-2016, 10:34 PM by Radioroslyn.)
(07-07-2016, 10:31 PM)Radioroslyn Wrote: I was right the hole was too small to fit the socket from the top so I enlarged the hole about 1/32" and was able to get it in. But now the issue is that the chassis thickness makes in darn near impossible to fit the retaining washer in place. So now I'll have the enlarge the hole a bit more so I can fit it from the bottom with the mounting bracket underneath. Removed the other 42 socket too so I won't have an arcing problem from the other socket.
Hey Ron tell Deb that I just finished the last brown sugar/cinnamon cookies , they stood the test time! Found a few after digging though some of the stuff that I came back with.
Terry
Are you sure that the wavy retaining ring won't work? Some of those are a bit tricky to get on, you have to sort of feed the ring into the groove, spread the ring, and push down at the same time, with some small flat bladed screwdrivers. One problem that you may run into is that the hole in the chassis has no key to stop the socket from spinning, so what I did was use some Permatex glass and windshield adhesive around the bottom of the socket flange.
In my case the socket holes were too small as well, but rather then making the chassis hole smaller I mounted each socket in a Unimat lathe and made them slightly smaller by maybe .020'', I figured that it was because they were Soviet/Russian made octal sockets manufactured in Metric rather then U.S made Amphenol ones. Bakelite is a lot easier to grind down then steel plate.
Regards
Arran
(07-07-2016, 10:31 PM)Radioroslyn Wrote: I was right the hole was too small to fit the socket from the top so I enlarged the hole about 1/32" and was able to get it in. But now the issue is that the chassis thickness makes in darn near impossible to fit the retaining washer in place. So now I'll have the enlarge the hole a bit more so I can fit it from the bottom with the mounting bracket underneath. Removed the other 42 socket too so I won't have an arcing problem from the other socket.
Hey Ron tell Deb that I just finished the last brown sugar/cinnamon cookies , they stood the test time! Found a few after digging though some of the stuff that I came back with.
Terry
Are you sure that the wavy retaining ring won't work? Some of those are a bit tricky to get on, you have to sort of feed the ring into the groove, spread the ring, and push down at the same time, with some small flat bladed screwdrivers. One problem that you may run into is that the hole in the chassis has no key to stop the socket from spinning, so what I did was use some Permatex glass and windshield adhesive around the bottom of the socket flange.
In my case the socket holes were too small as well, but rather then making the chassis hole smaller I mounted each socket in a Unimat lathe and made them slightly smaller by maybe .020'', I figured that it was because they were Soviet/Russian made octal sockets manufactured in Metric rather then U.S made Amphenol ones. Bakelite is a lot easier to grind down then steel plate.
Regards
Arran
Are you sure that the wavy retaining ring won't work?
Well I was thinking in my simplistic mind that it would easy just to snap those rings in and be done with it be but on this thing you need to be an octopus with a hand full of pliers and small screwdrivers. And wouldn't ya know it my lathe is on summer vacation!
The other socket is mounted under the wire wound bias resistor. If I remove it the bracket is kinda in the way still.
Yes there isn't a keyway I was going to just use a heavy gauge piece of wire soldered to the heater ground terminal and fasten it to the chassis.
The dremmel makes pretty quick work of enlarging the hole. Takes 10 minutes or so. Seems easier to do this than fooling with the groove in the socket and try to get the clip in place.
Then back to the osc problem.
Looking forward to your first power up.
