The Mercury
 

Model 4188. Chassis 101 It uses the 12LP4.

This doesn't even appear in my Sams index, anyone know if there is a sams for this, if so I probably have it, if not does anyone have a schematic or know where to get one?

The finish really isn't as nice as in the ebay pics. Vineer is bad in places too. Some sets are clearly nice enough to leave the cabinet as is, others definetly need work, this is one of those sets where it's somewhere inbetween. I wish I knew more about repairing vineer, anyone recommend a good book or other source of information on the subject, I got a few other sets that need vineer work too. And the finish on this is odd, it's not really a clear finish, more like fake yellow wood grain painted on. Any thoughts on what it is?

The good stuff is that it's complete with both the back and the HV cage cover which are almost always missing from sets of this era. And it's like new behind the doors, the cloth is is excellent condition, all original knobs there. CRT tests good.
Here's some pictures...

Adam:

I'm glad that you got that set. I probably have the schematic and I can help you out with the finish as well. Sent me a PM or email.

Steve

I looked up the 12LP4C, and it's listed as an aluminized tube that still requires a double field ion trap.

Hey Adam

Glad you got the set! If it were me I would leave the finish "as -is" as it will be very difficult to duplicate that blonde type finish or to touch up, I would paste wax the finish using the Johnsons paste floor wax to give it a decent shine, I bet it would display decently. To re-finish it in a dark stain would be awefull and very hard to do the blonde! The veneer chip does not look too bad, is there others that are bigger? I see the RCA type channel knob, does it have "channel one"? Good luck!:thmbsp:

Doug:

Adam brought the cabinet up to my place a few days ago and the original finish was too far gone to really make it look good. The original finish, as seen inside the doors and around the CRT, is a fairly yellowish blonde the was more of a paint than a stain. I was able to come fairly close to the original look using a combination of stains and lacquer.

BTW Adam, I want to fix that broken foot yet and it should be ready tomorrow.

Steve

With that knob I thought it had channel 1 too, but it doesn't. It's actually kind of a strange tuner in that it doesn't go all the way around it stops after 2 and 13.

Cool set! Interesting pink quilted fabric around that picture tube.

Is that late 1940s-early 1950s vintage?

Can't wait to see pics of it "fired-up", Adam !

Not just RCA type knobs but that chassis is VERY close to the typical RCA chassis of that vintage (late 40's to very early 50's). The differences I see are the lack of the long 3 in 1 bias network, flter resistor that the RCA's are known to have troubles with, and the control positioning looks different. The basic chassis and most of the tube positioning I can see looks nearly identical right down to the 12LP4.

Here is the cabinet after Steve K refinished parts of it. It looks good. Inside the doors is 100% original finish, the new stuff is on the outside.
It is similar to the RCA's, I'm going to fix up my 721ts next because I haven't ordered any caps for this one yet, so I'll be able to compare the two.
I'm not sure of the exact year, I think it must be '48-'50.

Very Nice Adam!....Very good job Steve :thmbsp: looks wonderful! Have you powered this set up at all? I cant imagine very many Mercury sets around though it was made locally, just like the Kaye-Halbert that seldom show up though again made here locally.

I finished recapping this, but it's not working at all, no (or very little) HV no sound, no nothing. The filaments do light. I tried messing with the ion trap just to be sure it wasn't that, but if I go to discharge the 2nd anode after the tv was running, I don't see any sparks, so I'm pretty sure my problem is no HV. Now the power transformer is making some kind of buzzing noise, but I checked the voltages in the power supply, and it looks ok. I also hear the yoke ringing when I turn the horiz hold control. I checked the 1 meg resistor in series with the 2nd anode, and it tests good. I checked voltages on the HO tube and the damper, but the schematic I have is not the same as what's in the set, even though it says it's for this model, so I don't know if I should trust the voltage numbers on there. I'll draw over my schematic to show what's in there, then post it later.

I went and tested the HO tube, h osc tube, damper, and HV rect, HO tube tested a bit weak on the emission test but showed a lot of heater cathode leakage, horiz osc only slightly weak, damper tested ok but also showed alot of heater to cathode leakage, and 1B3 was weak. So I just went and swaped all of them at once to see what would happen, the picture tube lights up strong now, HV is good. I didn't have a 12AU7 (horiz osc), so I swaped it with a modern equivalent, a ECC82, I hope it will sync. I didn't have an antenna hooked up before, so I couldn't tell, now I'm going to go back and try. Power trans is still buzzing, I sure hope it doesn't short out, this set uses an unusual 2 tube power supply (5U4 and 6X5), so a replacement won't be easy to find.

The horiz doesn't sync, but it's the same with both the original tube and the new tube. But vert sync is fine, at least I have HV and I know the flyback is good.

Fixed the horiz sync, it was a bad resistor, had to put 2 in parallel to get the correct value, I'll have to get the correct replacement tomarrow. The ECC82 didn't work as a replacement for the 12AU7, but I put the original tube back and it seems to work. I left the new HV rect, damper, and HO tubes in.

All working now, although it does seem to show more retrace lines than most sets. And that noisy power transformer still worries me, but it seems to be working ok. Here's a pic of the set working, yet another pic of the bewitched Zenith...

I'd like to find a replacement for that buzzing power transformer (and maybe also the choke coil, it just leaked out a lot of wax and the set was only on for about 30min) anyone know where I might possibly find one? I don't have a part number, but here's a pic off of the schematic which gives resistances between and the voltages at the different taps on the coils...

Here's pics of the chassis:

The part number for the power transformer on the list stuck on the inside of the cabinet is 5000, if anyone can cross reference that to anything.

The horiz sync was weak and I just fixed that by swapping out one of those micas, but after watching it for a few minutes after that the power transformer finally crapped out. When looking for I replacement, I'm not entirely sure what's going on in this power supply, I understand how the 2 seperate rectifier tubes are working off the same coil, but what I don't understand is how this -2.5V source is working: is the center tap on this transformer actually slightly over to one side and not in the center at 0v?
But then if the center tap was off center I don't think the output voltage of the power supply could be made constant, as each time the AC changed direction the voltage going into the rectifier tubes would higher or lower, so then maybe the -2.5v just has to do with a voltage drop across that 10 ohm resistor and that center tap is right in the middle of the coil at 0v, although that doesn't seem like it should be possible to be both 0v and -2.5v, I'm still confused...

Adam:

The center tap is centered. You are measuring the B+ from ground and, you are right, the tap is seperated from ground by that 10 ohm resistor which makes it negative with respect to ground.

Steve

I get it just because its -2.5v in reference to ground, doesn't mean it can't be 0v in reference to itself. Thanks. I hope I can dig up a replacement after all the work that went into this set.

Adam, What is the model number on the Mercury? It looks very much like a '630 clone chassis, and if so, finding a powrer transformer and choke should not be a problem. I can look up the part # crosses if I have the model #.

The model number is 4118, chassis 101. Thanks for looking that up. I pulled out a 630 schematic (I have a 630 in a cabinet that needs alot of work I wouldn't mind parting out to fix this) but I don't think the power transformer from the 630 would work, it uses 2 5U4s in parallel, whereas in this set the secondary is actually tapped in 5 places 360v-175v-0v-175v-360v, and the 5U4 hooks to the 360v, while a 6X5 goes to the 175v. There's alot of similarities between this and the early RCAs, but where it's different is in the power supply. I seem to remember seeing some early Admirals with something like this though.

Adam:

Some of the early Admirals did have power xformers with seperate windings for a 5U4 and a 6X5. The voltages were a bit lower than what your set calls for but it should still work.

Steve

I was looking through my sams trying to find a part number for this transformer, and it turns out that Pacific-Mercury was using Sears' chassis, here's a pic of the corresponding Silvertone set from the sams. Silvertone model 9123, Sams 76-19, power transformer: Silvertone A1098, Stancor P-8157.

new power transformer
 

I have my new power transformer, Merit 3053, which crosses to Stancor P8157 which is the unit the sams says to use as a replacement for Silvertone models 9123-9126 which use the same chassis as this set.

Now the sams says when using the Stancor replacement to use a resistor to drop the voltage, and now I see why, the original transformer was tapped at (according to the riders schematic) 360-175-0-175-360, (according to the sams) 390-175-0-175-390 the Merit replacement is 375-325-0-325-375. So I don't see the 375-0-375 for the 5U4 to be a problem, but I'm going to have to drop the voltage comming out of the 6X5, I would assume that the best place to add the extra resistor would be right after the filter capacitors, also I would think a 5W resistor would be enough, but I'm not sure what resistance to use. And I don't want to connect it all up with too little resistance in there and burn something out, and if I just put resistors in there and then check the output voltage with out anything hooked to the power suppy, because it won't be drawing much current the voltage reading I'm going to get will be way higher than it actually will be with everything connected so I can't figure it out that way. Any ideas?

Also for the filaments this transformer has two 5v secondaries and two 6.3 volt secondaries, I can either just use one of each and get 5v@3A and 6.3v@7A or parallel them and get twice the amps, 5v@6A and 6.3v@14A which way should I go?

I would locate the resistor right after the 6X5, that way you keep the voltage on the filters to a minimum. The max DC current for the 6X5 is 75mA, so (325-175)/.075= 2000, and 11.5 watts, as a worst case.
At 5000 ohms, 150/5000=30mA, and 4.5 watts. I would try the 5K ohm 5 watt resistor. Bring it up on a variac and monitor the voltage, and adjust the resistor value and wattage as required.

As for the filaments, try to keep the current rating and the actual load close to each other. Paralleling the outputs when you don't need to will make the filament voltage run on the high side. You may have to add up all the tube load currents by hand to determine your actual requirement if Sams does not give it.

Good luck.

[QUOTE=Adam;1243909]Model 4188. Chassis 101 It uses the 12LP4.

This doesn't even appear in my Sams index, anyone know if there is a sams for this, if so I probably have it, if not does anyone have a schematic or know where to get one?

It is listed as Model 4118 Ch. 101 in the Rider TV index in Vol. 5-1. I can scan this to a .pdf and email it to you in two pieces that will overlap. Just send me a private message with your email address in it.

Also, I have only the cabinet for a SIlvertone 10 inch set that is laid out the same as your set is. The center knob is lower than the other two and the knob functions are just the same as in your pic. Did Pacific Mercury OEM sets for Sears? It sure looks like they did.

Cliff

Watch that 6X5, they are prone to arcing and shorting, probably responsible for taking out more power transformers than any other tube in old radios. If you're going to use a 6X5 get one of the newer style with the X type plates similar to the internal construction of the 6X4 they are much less likely to short than the older styles especially the ones with the close spaced parallel plates.

Thanks to everyone who posted here for all the help on this. There already is a resistor 100ohm 4W inbetween the 6X5 and the filter caps, so I'll change it out for one around 5k 5W. According to the sams the 5v winding should be at 3A , and the 6v at 9.1A, so I can just use 1 of the 5v windings for 3A, but the 6v will either be low at 7A or high at 14A.

It already has one of the newer type 6X5s in there which I checked for shorts. I think the demise of the power transformer was caused by the people I bought it from plugging it it to see if it works with shorted filter caps. I don't see many of the older type 6X5s, I just looked in my stash of tubes and only 1 out of 5 6X5s I had was the old type, they've probably mostly all shorted out by now.

I already picked up the riders, and the sams corresponding to this is not listed in the index, but the Silvertone models 9123-9126 do use the same chassis, so you can find it in sams 79-16. I'm not sure if it was Sears making chassis for Pacific-Mercury or Pacific-Mercury making them for Sears though. But then this set did use Silvertone tubes.

If it were me, I think I would use two resistors (of half the needed wattage), and put them in the plate lines of the 6x5. Those were/are a problem tube.

I don't have the sams, but usually the 6x5 filament is run from the same 6.3 volt winding as all the small tubes in the set. If this is the case, usually one side of that winding is grounded, and therein lies the problem.

In a typical 6x5 setup, there is full b+ on the cathode, and the filament winding is grounded. A typical failure is a heater-to-cathode short that burns out the power transformer. It wouldn't surprise me if this is what happened to the original transformer.

The main thing is that white goo on the filament has to hold back b+. A 6x5 apparently wouldn't even hold to it's rating, let alone more. IMHO putting more voltage here is a really bad idea.

If the 6x5 has its own 6.3 volt winding that floats above ground, you can disregard all this ;)

John

Originally, the 6X5 does go to the same 6.3v winding and to ground as all the other tubes. But this new transformer has two 5v and three 6.3v filament windings, so I could change that. Two are 5v 3A, two are 6.3v 7A, one 6.3v 2.7A with an extra tap in the middle for 5v. Originally the sams says it requires 9.1A on the 6.3v filament winding. I suppose I could take the 6X5 and hook it to the 2.7A winding, and keep all the others on a 7A one, but then the 6X5 might be getting too much power, and the other tubes not enough?

Did you say there is a third 6.3v winding? How many amps is that? If theres only two, it would seem they intended you to hook the two windings in parallel in phase to get the extra current capacity.

It is WAY better to have a separate filament winding floating for the rectifier. If you've got an extra 5 volt winding, you could use a 5 volt rectifier tube like a 5z4. This is a cathoded tube like the 6x5, but the cathode is connected to the filament, so it requires a separate filament winding. Another good solution might be a 5y3. These have a bunch of internal voltage drop, and your dropping resistor(s) would not have to dissipate as much heat.

I like to keep things original though, and so would probably keep the silly 6x5, even on a grounded line if it was the only way.

It seems you have a bunch of windings. What is the voltage of your primary winding? 117? Do you have any primary taps? Whats your line voltage? Mine is 121V.

Heres some food for thought, based on whats currently on my bench. You kinda hit the nail on the head with your comment about the 6x5 possibly having too much filament voltage.

On the old comms receiver I'm currently working on the power transformer had been replaced, and everything was running too high. I had an extra 6.3v winding, probably intended for a damper in an RCA TV chassis. I connected it in series with the primary, phased in such a way to reduce all the voltages. This brought the 5.0v and 6.3v lines back down to normal. The b+ is still too high, but only by about 25 volts. I'm gonna drop that with a resistor.

I would get the filament voltages right, and then do whats necessary to correct the b+. Maybe a winding of some kind could be used in series with the primary like I did, if everything is too high. If a fairly big 5.0v winding was unused, it might run high enough for the 6x5. You can also usually get away with overloading one secondary winding a little if you are not using all the others. If you overload it the voltage will probably come down a little.

Is the replacement transformer tapped like the old one, or is the 6x5 b+ winding separate?

The old transformer had 3 secondaries: 360-175-0-175-360v 195ma/40ma, 5v 3a, 6v 9.1a.
The new one has 6: 375-325-0-325-375v 170ma/130ma, 5v 3a, 5v 3a, 6.3v 7a, 6.3v 7a, 6.3-5v 2.7a.

One of my concerns is with the 6.3v filament winding, it seems if I just use one 6.3v 7a winding the current is too low, if I parallel them it is too high. Now as for the 6X5, if these rectifier tubes using a cathode are such a problem, I could take the 2nd 5v 3a winding and put in another 5U4 instead, I would think a 5U4 would work better than a 5Y3 because isn't a 5Y3 only a half-wave rectifier.

Actually no, a 5y3 is an 80 with an octal base. It's a full wave tube. It's also extremely common and cheap.

There isnt a problem with cathodes specifically, but most rectifiers that have them have the cathode hooked to the filament (5z4, 5v4,5ar4,etc), so a sepatate filament winding is needed just as though it didnt have a cathode.

The real reason for using a rectifier with a cathode is voltage drop. All else being equal, there will be less voltage drop across a cathoded rectifier. This leads to less 'sag' under load. This is generally considered a good thing, but in your case you need to lose all the voltage you can.

Either a 5y3 or a 5u4 should work fine, but if I was going in that direction I would use the lossiest tube I could find. 325 volts is WAY too high. You'll have to look in a tube manual, but I'll bet the 5y3 is gonna be the lossiest one. Any extra voltage you dont lose in the tube, you will have to dissipate with a resistor.... so you might as well lose all you can in the tube.

Heres what I think I would do. Leave the 6x5 for the moment. I would hook one of the 6.3/7a windings in parallel with the 6.3v/2.7a in phase. This is 9.7 amps for the 9.1 amp winding. not too bad. Use one of the 5v/3a windings for the 5u4. This leaves you a 6.3/7a and a 5v/3a to play with.

I would then temporarily scab some resistors in the plate lines of the 6x5. 4.7k at about 5 watts oughta do it. Run it up on the variac, and see how far off everything is. If everything is too high, (and It probably is) you can use one or both of the extra windings to "extend" the primary.

If you have any windings left now, you could use one for the 6x5 (or 5u4 or 5y3).

John

Now I've tried numerous combinations, the 360v volt source hooked to the 375v secondary of the transformer going to the 5U4 is right on at 360v. The 6v filaments are hooked up to the 2.7a and one 7a winding in parallel and that seems to work, it actually runs some tubes a little high at 6.5v, but it seems ok. The second rectifier is currently wired for a 5Y3/5U4 (they have the same pinout), using the 2nd 5v 3a winding. I figured why deal with the 6X5 if they have a history of shorting out, even if I could wire up a seperate power source to the filament so it wouldn't take my new transformer with it.
Using 2 4.7k 5w resistors to the plates and a 1k 5w resistor before the filter capacitors, the voltage was too low at around 100v, with no resistor before the filters and 4.7k before the plates that went up to around 110v, with no resistors before the plates and 1k before the filters around 190v, with no resistors before the plates and 4.7k before the filters 120v. Switching between the 5U4 and the 5Y3 only made around 5-10v difference. I think next I'm going to try around 3k before the filters, no resistors before the plates with the 5U4 (I like the way those 2 big 5U4s look in there), and also go up to 10w, the 5w resistors were getting on the hot side, not the ones before the plates, but the ones before the filters.

Sounds like a good idea. Since you're using a 5u4, theres really no good reason to have resistance ahead of the plates. The whole Idea there was to keep the heater to cathode voltage on the 6x5 from being any higher than it was originally.

Keep us posted :)

John

I ended up using a 2.2k 10w resistor before the filter caps with the 5U4, with that it produced around 155v after the set was warmed up. Here's some pics...

Looks great. Nice picture! :thmbsp:

John

All back together, thanks again for everyone's advice and help on this set, this was a difficult one. Here's some pics of it back together. I took a pic with the back on because this is the oldest set I have that still has (at least most of) the back...