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Meck XB-702 restoration
I was recently contacted by a member of ARCI (Antique Radio Club of Illinois) to see if I was interested in a late 40s 7" set - model unknown.
https://live.staticflickr.com/65535/...a5c490e6_c.jpg I was happy to make a solid offer as there was no radio swapfest this year and the proceeds help fund the club. I also got a tour of his excellent collection and basement workshop. Was able to see some high end radios I'd only seen in photos previously :) He sent some photos including the cover of Sams showing a Meck XA-701 that looked similar. A little detective work and thanks to Riders vol #3 I think we have a positive ID as a model XB-702. There is a label inside but the model was trimmed off. https://live.staticflickr.com/65535/...91e7b613_c.jpg First the good. All knobs and present and the chassis appears to be 100% original. Even all four rubber feet are intact and in good condition. Have not tested the picture tube yet. https://live.staticflickr.com/65535/...40fb0c92_c.jpg https://live.staticflickr.com/65535/...f913a08e_c.jpg Now for the bad. It appears to have been stripped using a belt sander that wore through the veneer in a number of places. At least if I do decide to replace it, it's basic mahogany crosscut veneer. https://live.staticflickr.com/65535/...10eb671a_c.jpg https://live.staticflickr.com/65535/...22b48f67_c.jpg |
Appears to has seen some heavy use. Most of the caps show sings of deterioration.
https://live.staticflickr.com/65535/...1637521b_c.jpg https://live.staticflickr.com/65535/...93dcb789_c.jpg I dig the high voltage caps and will try to restuff them. https://live.staticflickr.com/65535/...2af7a8a9_c.jpg Apparently Meck cut a few corners to keep costs down. There is no AC interlock for example and the power supply is crazy. Similar the the Halicrafters 505. A 6X5, 25Z6 and a selenium for a total of 5 rectifiers producing -120V, +120V, +250V, +300V and +350V. https://live.staticflickr.com/65535/...d15a5d72_c.jpg |
You lucky dog you! LOL I live about 20 minutes from Plymouth Indiana where that set was made and I've been looking for one for the better part of 40 years and here you find one... I'll be interesting to watch are you planning on doing videos? If nothing else I can always drool and dream LOL
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I have a Meck XA-701 that I restored, that chassis looks very similar to mine.
It’s on YouTube, here’s the link If anyone’s interested 1949 MECK 7” TV Restore Part 1 of 4 Analysis and CRT Testing https://youtu.be/7gSGcUju_jM |
I got it up on the backup workbench last night and tried a controlled power up. I was able to squeeze a very dim raster out of it. No change in image or sound when channels are changed.
https://live.staticflickr.com/65535/...9c0770f5_c.jpg https://live.staticflickr.com/65535/...16274b22_c.jpg Every single axial electrolytic has dry, crusty goo coming out so I expect that are all very bad. I'll tackle the power supply first. |
I've got a 1950 Philharmonic (Meck) Model 8200 10" TV that I had finished restoring electrically a couple of years ago, the Philharmonic Model 8200 was basically a Meck XQ-776 TV (the Philharmonic nameplate was due to Meck Industries buying out E. H. Scott in late 1949 which was who originally owned the "Philharmonic" nameplate.)
My TV was bought from someone locally who picked up the from inside an old Farmhouse in Mishawaka, Indiana that the roof had collapsed on it over 20 years ago and the solid walnut cabinet was still in excellent condition yet considering the conditions the TV was stored in for a while, I stripped and refinished the cabinet myself. |
Very nice. I recall following your restoration progress.
I was a bit disappointed to discover those nifty CCC high voltage caps are actually old replacements. I snipped them out and tacked in replacements. That improved the raster quite a bit. I also found that the main B+ rail was only about 75 volts. I tacked a 1N5408 diode across the selenium rectifier and that brought it right up. No noticeable improvement though. Loud buzz out of speaker and no hint of reception. I'll continue to work my way through the power supply. https://live.staticflickr.com/65535/...c69f0f37_c.jpg |
What a cute little TV. I like the simplicity of the cabinet. It reminds me of a simplified National TV-7W.
It's too bad they used a belt sander of it to save a bit of time refinishing. Someone done that to my GE 10T4 also. |
Replaced a few more caps in the power supply with no improvement so I turned my attention to the tubes for a while. It's a rather curious mix.
First, we have one 25Z6 and two 6AL5s branded with MECK https://live.staticflickr.com/65535/...1234e4cb_c.jpg https://live.staticflickr.com/65535/...0f1846c8_c.jpg All of the remaining octals are RCA with the same '9-26' date code. 26th week 1949 ? https://live.staticflickr.com/65535/...73601f04_c.jpg Then a bunch of MIRROR-TONE branded 6AU6s dated '9-35'. I don't recall ever seeing this brand before. https://live.staticflickr.com/65535/...7b1beee6_c.jpg They all test very good. Could they all be the original tubes? Also found this label inside. The original owner? https://live.staticflickr.com/65535/...cd197eea_c.jpg |
Based on all the tubes appearing to be original from 1949 and testing strong I would think it was a low hour set. However, all the caps look like hell.
They are all either made by the Industrial Condenser Corp or Chicago Condenser Corp which is still in business today. Which leads to another mystery. The four HC deflection coupling caps have clearly been replaced. They are wired with clunky "j-hooks". However, they appear to be as old as all the other caps and are also made by CCC. Could they have failed shortly after the set was sold and replaced under warranty by Meck ? https://live.staticflickr.com/65535/...798711c4_c.jpg https://live.staticflickr.com/65535/...fd5f121d_c.jpg |
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I believe my Meck TV which had many of the original caps in it yet had mostly Chicago Condenser Corporation Capacitors in it, I believe they were a very common supplier of components to a lot of Midwestern electronics manufacturers in the 1940s-1960s in fact my 2 Zenith TVs I'm currently working on also had Chicago Condenser Corporation Capacitors in it as well (specifically my "Bugeye" TV, I also had a ton of those in my Zenith Bugeye clock radio and also in my Zenith 10S690 (which has long since been scrapped because I couldn't fix the turntable drawer because I couldn't find any drawer glides that would fit the turntable drawer properly.)
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I replace the four HV deflection caps and got a full raster.
Then, I finally realized I had made a stupid assumption that the channel #s went clockwise. So instead of tuning to my RF signal source on channel 3, I was tuned to channel 12! https://live.staticflickr.com/65535/...6a994142_c.jpg I might have had a picture form the start. We'll never know. The loud audio buzz was caused by a bad cap between the volume control arm and the grid in the audio preamp tube. Somehow that was causing the high impedance circuit to pick up all surrounding EM radiation. Just moving my hand near the cap cause all sorts of noise. Replacing the cap resulted in OK sound, but it's way off from the picture. Odd considering this is an intercarrier IF set. The 4.5 MHz pickup coil must be misaligned. https://live.staticflickr.com/65535/...6aa5cb1d_c.jpg The focus and centering controls are acting flaky now so I'll pull the phenolic sub-assembly out for a going over. I figure there could be tin whisker or gunk attracted by the static charge. https://live.staticflickr.com/65535/...0a9f1a1b_c.jpg |
Ugh. Replaced a few more paper caps and lost reception. That happened once earlier and wiggling the 6C4 tube in the tuner got it back, but not this time.
The channel selector is also very stiff. I need to get in there for a clean and lube. Haven't quite figured out how to get the shield off yet. |
Rookie mistake. I was interrupted while recapping and forgot to install a new coupling cap between the video detector and video amp :withstpd:
My recently refurbished Tek 454A scope quickly pinpointed the problem. Recapping is now done on the IF and video circuits and the image is lousy. Also, the tuning is one channel off and sound/video are mile apart on the fine tuning. An alignment is definitely in order. Also, bad horizontal fold over if I increase the width. Still need to finish recapping the sweep circuits. https://live.staticflickr.com/65535/...f242b7ef_c.jpg |
It turns out my width issues were due to 1/2 of a 12SN7 going dead. Absolutely 0 emissions. I figure the cathode must be open.
Next up, I pulled the tuner for an overhaul. Now, I can see that it is a Sarkes Tarkian V5941 made in Indiana. It does not match the service info and the output wire is spliced into the set. That makes me wonder if it's a replacement? Maybe at the dealer when they replaced the HV caps? It could also very well be that the mixer tube really should be a 6AU6 and not as 6AG5 as shown in the tube layout? I tried looking up that tuner part# but came up empty. https://live.staticflickr.com/65535/...24d4a558_c.jpg https://live.staticflickr.com/65535/...c0e0d4d6_c.jpg |
New caps have arrived for restuffing :)
https://live.staticflickr.com/65535/...10c1da06_c.jpg I also tried out some GoJo on the chassis. It does a fantastic job removing the baked on crud. The cleaned metal gives off a black residue though. As if it's immediately oxidizing on contact with air. The gray on the paper towel is the dirt. The black below it is from wiping a few minutes later. The paper towel also leaves very fine scratches on the metal. I've rub down the chassis with BoeShield T-9 once it's cleaned. https://live.staticflickr.com/65535/...2eeacaa6_c.jpg |
You're sure making progress quickly Bob. We're lucky capacitors have gotten smaller over the years do we can restuff them. Are you going to do the wax paper ones as well?
If there is Sodium Hydroxide you will get the black oxidation afterwards. I don't know if there is any of it in Gojo though. I went hunting for information on that tuner and also came up empty. Can you make out what year is on the date code? |
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Yes, I will be restuffing all the paper caps. Ah-ha, I be there is some sodium hydroxide in it. I think the month is Aug, but the year is smudged and illegible. |
This chassis is so light I'm able to use this radio chassis stand while working on it.
https://live.staticflickr.com/65535/...12ccf169_c.jpg My plan is to restuff the caps and I went after the elctrolytics first. I had a heck of a time getting the covers off the electrolytics using a heat gun. They used a crazy amount of tar and I ended up tearing open the side opposite the printing. I'll either salvage these or make replicas https://live.staticflickr.com/65535/...89bea5ca_c.jpg https://live.staticflickr.com/65535/...1bf1f627_c.jpg |
I managed to get all the cans cut open and restuffed using a mini hacksaw and a little pin vice drill.
https://live.staticflickr.com/65535/...72a81c8d_c.jpg The image is somewhat improved but dim. I have not recapped the HV box yet. This is with a 6AG5 in the tuner. Will next try with a 6AU6 as was in the set when I got it. https://live.staticflickr.com/65535/...6639354d_c.jpg I was planning on moving the speaker to the left side but discovered the mounting holes don't line up. Also they are not tapped. Clearly nothing was ever mounted on this side. https://live.staticflickr.com/65535/...77a870f2_c.jpg https://live.staticflickr.com/65535/...8a46a50d_c.jpg |
I decided the mount the speaker on the left. It's obvious the wires were cut and extensions added. I just have it mounted in one hole for now.
There's a bit of undulation in the vertical . I figure some 60Hz ripple is sneaking in. https://live.staticflickr.com/65535/...d2536471_c.jpg |
Next up I worked on the RF HV supply. It is contained with the black metal box on top of the chassis. I needed to remove four nuts from below to unmount it. Luckily, there was enough slack in the wiring to tilt it back on work on it.
The variable capacitor adjusts the output voltage. I tweaked it to get 5kV as per the service info. https://live.staticflickr.com/65535/...b31d5314_c.jpg |
Are those restuffs too?
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No, that's the before picture. I didn't bother restuffing these caps since they're so hidden away.
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The picture is looking a lot nicer since you first started. Looking forward to seeing the results after the HV recap.
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It helped get the HV up, but the raser size decreased. I suspect I have some resistors that are off in the HV divider string.
I'm going to go through and do all the restuff next. Heat gun to melt out the old cap. Brown hot glue to seal the ends. Satin wipe-on poly to seal it. https://live.staticflickr.com/65535/...f2ebfda8_c.jpg |
I never knew about brown hot glue. That's brilliant.
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Thanks. I like that I can reflow it with a heat gun if I mess up. I'm about half done with the paper caps. Then, I'll move on to the half dozen axial electrolytics. I think those are the most challenging.
https://live.staticflickr.com/65535/...6920444f_c.jpg |
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Much lower temps. A glue gun won't melt the capacitor or pvc wire insulation. I got these off eBay years ago. Many, many places carry them. Amazon, etsy, etc.
Just be careful you get the right size - mini vs full. https://www.etsy.com/listing/2589412...lue-sticks-for Heck there's even hotmelt.com https://www.hotmelt.com/products/inf...nt=25974897099 |
Inevitably I was going to find some out of spec resistors. The two 47K horizontal amp plate resistors are over 100K. Luckily, I have a limited stash of NOS carbon comps. I found two that are about 50.8K. That's only about 10% high and they match each other so I'll use them.
https://live.staticflickr.com/65535/...06742577_c.jpg |
The final caps to rebuild are the axial electrolytics. I carefully un-knurl the negative end of the cardboard tube and push the cap out.
The can is thin, soft aluminum - very easy to cut through. I then wash out the insides and drill a small hole in either end. Then a little hot glue to close the can back up. Finally, I knurl the cardboard tube back over and use a little glue. https://live.staticflickr.com/65535/...57fbc19d_c.jpg |
Here's the rebuilt cap. I do have trouble with paint flaking off the resealed end. Perhaps it could be touched up with artist acrylic paint.
https://live.staticflickr.com/65535/...c9fe848a_c.jpg https://live.staticflickr.com/65535/...2e67a1bd_c.jpg |
Maybe the careful application of a small bead of your brown hot glue would dress it up a bit ?
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Perhaps. I just left them as is for now. I finished up the sweep and audio amp side. While doing so, I replace 5 resistors.
The end result? Loss of height and bad horizontal linearity! Now there's still a lot more work on the other side so I'm not too concerned yet. At least it looks nice :yes: I did some quick spot checking and am finding more than half of the resistors in the IF and sync circuit are way off. 50%-100+% high. That's going to take a while to do :sigh: https://live.staticflickr.com/65535/...4b8b020b_c.jpg |
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I restocked by axial film capacitor stock using JustRadios. Was surprised to see the white HV caps are SHV rather than ASC. A new player in town?
I'm just happy they are available somewhere from someone. https://live.staticflickr.com/65535/...b2f5a5d3_c.jpg |
I picked up a bunch of 1.5" diameter cardboard tubes for new capacitor covers. I can cut them down and paint as needed for this and future projects.
The one think left to figure out is a good method for sealing one end. The originals were knurled over and had a cardboard disc glued in. https://live.staticflickr.com/65535/...0b469359_c.jpg |
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