Roadside p/u Motorola SK80CW (Help needed)

[TC Chris]

i have restuffed and I have left the can intact and added new caps under the chassis. It depends on available space.

I have a 1948 Wurlitzer jukebox that has original filter caps. That's probably pushing my luck, although I bet that the heavy-duty service of jukeboxes led to use of better electrolytics originally. The jukebox needs a bit of mechanical work and probably an upgrade of the filter while I'm at it.

Chris Campbell

[SSGNDoc]

Looking into things a bit more over the weekend I sent for an estimate for a “built” canister capacitor from Hayseed Hamfest. Quote comes back at $44. The corner of the chassis where that capacitor mounts, looks a little crowded. So, not sure space wise if replacing it with multiple capacitors underneath more cost effective with enough space.

I’ll update with a few more pictures tonight after I get home from work. To include some info on the record changer.

[SSGNDoc]

With regard to the record changer, here is a picture of the ink stamp on the underside. If I’m understanding the deciphering of the numbers based on what I saw at the Voice of Music website, the record changer is made the 14th week of 1963, and the model number would be a 1242.

I know the cartridge takes a 9T stylus which has two sides for LP or 78 records. I’m pretty sure the cartridge is good, but also pretty sure I should buy a new stylus. The stylus alone is going to be around $20-$25. The cartridge appears to be made of unobtanium, and if one is obtainable would be priced pretty close to $100.

Here is the ink stamp on the record changer.

[electra225]

As to the filter caps, have you considered restuffing the old cans? You can cut the filter cap cans apart, remove the old guts, then add new caps to the cans, then put the cans back together. I personally would not pay $44 for repop filter caps for a console stereo. I think I still have pictures of restuffing a can here someplace if you would be interested.

It is good practice to determine whether the cartridge is still good. If the old needle(s) are present, many times it/they are good enough to test the cartridge. If one side of the cartridge is dead, you won't want to spend the money for a needle. You would have to replace the cartridge. There is possibly a more modern equivalent/replacement cartridge that would work if you need one.

[SSGNDoc]

Another question occurred to me on the record changer. What type of lubricants are used on these after my daughter cleans the dried stuff off. (She has laid claim to restoring the record changer.)

[SSGNDoc]

As to the filter caps, have you considered restuffing the old cans? You can cut the filter cap cans apart, remove the old guts, then add new caps to the cans, then put the cans back together. I personally would not pay $44 for repop filter caps for a console stereo. I think I still have pictures of restuffing a can here someplace if you would be interested.

It is good practice to determine whether the cartridge is still good. If the old needle(s) are present, many times it/they are good enough to test the cartridge. If one side of the cartridge is dead, you won't want to spend the money for a needle. You would have to replace the cartridge. There is possibly a more modern equivalent/replacement cartridge that would work if you need one.

I watched a couple of videos on restuffing a canister. I guess my issue is really being blind as to both, selecting the proper modern replacement capacitors, and knowing if they would fit. Then my next concern would be just flat out destroying the can. I don’t have any idea on the size of three 40 uF @ 400V and one 150 uF @ 50V capacitors.


The second point. The cartridge and stylus at least did make noise when we did the briefly powered test. I know appearances can be deceiving when it comes to electronics, but the wiring to the cartridge looks pristine, and the cartridge also looks quite nice.

when I went to the VM website and looked into the cartridge they had none, and it said, “no substitutions”. The stylus was similar. I have found a few sources for replacement stylus. The two sided type has diamond on one side of the stylus and sapphire on the other. One would think these would wear pretty well.

[TC Chris]

Modern caps are physically tiny by comparison.

When taking apart the changer, document carefully with photos, and maybe do it inside a large cardboard box to capture flying clips. Some day the ton or so of flying, missing parts will show up in my shop.

Chris Campbell

[electra225]

Also in a multi-section can, one of the caps is for cathode bypass. You could put the replacement under the chassis saving room in the can. You can also stack the new caps on top of each other.

[Hi-Fi-Mogul]

The second point. The cartridge and stylus at least did make noise when we did the briefly powered test. I know appearances can be deceiving when it comes to electronics, but the wiring to the cartridge looks pristine, and the cartridge also looks quite nice.

1. Your V-M 1242 record changer: 857 (VM EIA code) 143 made
the 43rd week of 1961.

I will upload the V-M 1571 manual which should have all the
functional charateristics of the 1242.

2. The V of Music has a Dual tip 0.7 stereo Diamond stylus
for the Sontone 9-T. (808-DD77)

That would be a great choice for longevity of play.

https://thevoiceofmusic.com/catalog/par ... ategories=

3. Post when your ready to break down the record changer, and I'll cue you in
to some good videos and a static photo servicing of a similar V-M 1200.

RE: lubricants. I use small amounts of Super Lube synthetic grease in the
appropriate locations of the changer mechanism.

Some parts of the changer should have NO lubrication.

After the motor rotor and bearing housing is cleaned with alcohol,
we recommend Zoom Spout Turbine oil, since the rotor/bearing gets
very warm in use.

Dollar store liquid de-greaser or ISP alcohol are good cleaning agents
for removal of all the old grease in the mechanism.

[SSGNDoc]

Where I am at currently.

Upon receiving the schematic for the HS 968 amplifier used in this set-up and downloading a guide on how to read schematics, (Yes I’m that person in that stage of trying to understand this whole situation), I am pretty convinced that the current can capacitor is not original. (Probably no surprise to all of you). What is installed is a 40uF/40uF/ 40uF/ at 400 VDC, 150uF at 50VDC - Can. What is specified is a
40uF/40uF/ 40uF/ at 400 VDC, 200uF at 50VDC.

Also it looks like, whoever did replace this Capacitor soldered in two of the twist lock tabs. (The other two twits locks appear to be broken off or removed but have some solder blobs that look like they are being used as grounds. I cannot get a view of the “arrangement” of the central tabs symbols to know what is connected to what capacitance and voltage. When I try to check capacitance with my meter 3 of the tabs read below 10uF and the 4th under 20uF. So…it is definitely no good. (But I’m checking it still in the chasis, and not sure if that is truly correct.).

In searching for replacement capacitors, I’m having some difficulty finding same spec caps in stock. I seem to be able to find 47uF @ 400v

So now I have more questions.

1. Where are these specs tolerant of some variation? For example, is a 47uF in place of a 40uF capacitor at the same voltage going to be ok in this type of audio application?

2. From the schematic it appears each of the capacitors would just have their negative leads go to ground and the positive leads attach to the appropriate wire connections.

It looks like I would still need to pull the Can even if I wanted to do an under-chassis bypass just so I can positively ID which capacitor leads are at which capacitance and voltage. I’m still not sure I want to try to restuff this can (If I can even get it out in tact. The solder that was used is both generous in quantity and seems to be quite hard and a bit resistant to melting with my soldering iron.).

[TC Chris]

It's safe to go over specs in both capacitance and voltage, within limits. The 40 mfd spec was an old standard; the 47 mfd value is a new standard value.

Most multi-section cans ID the lugs via symbols cut into the bottom insulation at the lugs--usually a square, diamond, and triangle (or maybe nothing for the 4th one). If you're unsure, trace back from the component that's connected to that tab per the schematic. Be aware that you are looking for electrical equivalence--sometimes two destination points, two solder lugs, are connected together and the cap may be connected to one of them that isn't physically at the point shown on the schematic, if it's electrically equal.

Chris Campbell

[electra225]

Try to imagine the schematic as a road map. The road map that shows how electricity flows thru the chassis. The power plug will be the entry point, then on to a fuse, if any, then on to the primary of the power transformer, with perhaps a small detour for power to the changer. There will be a power switch somewhere in the primary circuit. Remember also that the plates of the rectifier tube have the highest voltage in the chassis, typically the center tap of the power transformer is common negative. Refer to the schematic and follow it if you are unsure as to values of components you see in the chassis, if they look like they have been replaced in the past. If they are original and they differ from the schematic, then use what is in the chassis. Confused yet?

Just take it from the start then follow the schematic like you would follow a road map. Remember road maps, before the days of GPS?

[SSGNDoc]

Try to imagine the schematic as a road map. The road map that shows how electricity flows thru the chassis. The power plug will be the entry point, then on to a fuse, if any, then on to the primary of the power transformer, with perhaps a small detour for power to the changer. There will be a power switch somewhere in the primary circuit. Remember also that the plates of the rectifier tube have the highest voltage in the chassis, typically the center tap of the power transformer is common negative. Refer to the schematic and follow it if you are unsure as to values of components you see in the chassis, if they look like they have been replaced in the past. If they are original and they differ from the schematic, then use what is in the chassis. Confused yet?

Just take it from the start then follow the schematic like you would follow a road map. Remember road maps, before the days of GPS?

I remember road maps. A schematic is not quite like one. It doesn’t actually give geographic location, which could possibly be more useful to a newb like myself. But I understand that isn’t as efficient a way to diagram this sort of thing.

I did have some time off today and I did order replacement capacitors. I fear I may have made a mistake when I selected the 200 uF/50V, not realizing it, unlike the rest is not polarized. I don’t know if it will make a difference. I could only find it as an axial lead, where the others are radial leads. It doesn’t actually give look like I could get all of them inside the can but, would have to run a jumper wire from the far lead to get it down and through the bottom of the can. Not sure if that is a problem either. So… currently I’m in a holding pattern on reassembling the can.

also probably a stupid question. But since the can was done as a common negative, I’m thinking my negative leads could all go together, and they should be soldered to the cassis/ground. Is this correct?

[TC Chris]

You're on the right track. Yes, use an extra wire on the axial lead cap. If you run out of space in the can, you can probably find room underneath the chassis. Yeah, all the negatives can connect together and then to ground or whatever the schematic directs.

The schematic is an electronicroad map. Looks like you've got a Sams folder, their "Photofact" series, that also gives you the under-hood geography in photos. Just remember that the schematic shows electrical layout; a component may not be connected quite as shown on the schematic if there is another electrically equivalent connection point that is closer or less crowded.

Have fun!

Chris Campbell

[SSGNDoc]

The schematic is on the opposite page. Between the schematic and the photo “map” has been pretty helpful. I wouldn’t have been able to use the photo for wiring, the photo is much neater than the underside of the actual chassis.

Having both has been pretty helpful.

[TC Chris]

It can be helpful to make a photocopy of the schematic and trace things with a highlighter. Use copies so you don't disfigure the original.

Chris Campbell

[SSGNDoc]

I have this as a downloaded PDF file and have printed two complete copies of this service manual. The other handy part is the parts list that also breaks down what each of the parts is as well as most of the ratings of those electronic components (which can be hard to read on the schematic).

[Hi-Fi-Mogul]

A couple of tips you may already know.

1. Tube pin numbers are read looking at the bottom
of the tube clockwise.

The tube base usually will have small pin numbers molded
in the base underneath next to the pins.

Tubes usually are constructed with an open space between first and last
tube pins.

The pin to the right of the wide space will be Pin 1.

2. Tubes do not always have all of their pins electrically
connected internally.

You will encounter abbreviations such as NC and TP.

These are No Connection and Tie Point.

So these NC/TP pins may be used to conveniently
connect various wires going to parts of the circuit.

Sams Photofacts usually has these identified.


3. You may benefit from downloading or buying a
Vacuum Tube diagram/data sheet manual.

Tube manufacturers such as RCA, G.E. and Sylvania,
published their manuals.

A few online sources:

https://plymouthcolony.net/starcity/rad ... rvice.html

https://archive.org/details/technicalma ... 3/mode/2up

http://www.tubebooks.org/index.html

https://frank.pocnet.net/

[SSGNDoc]

Making headway on restuffing the can capacitor. I elected to only put the three 43uF/400V capacitors inside the can. I will place a 220uF/50V capacitor on the underside of the chassis. Waiting for that capacitor to arrive (I think I found a smaller one that I ordered, which should fit better.

I think it came out pretty ugly on the underside but not too bad looking up top. But the connectors were all pretty heavily covered in solder before I ever got into it. I did butcher up the lip of the can that retains the steel ring. But that won’t be visible.

[TC Chris]

Looks good....

Chris Campbell