Can you post a clear close-up of the coil? I just ran into such a situation. The fix depends on how the coil is made. If you can check continuity with your ohmmeter it may be OK, though.

Sending you a PM.

Ok... quick updates:

- I have snaps of the coil, but they'll have to wait until Tuesday; large photos aren't dial-up friendly :no:

- I've been de-rusting the chassis... a couple of spots that I want to take care of before they get bigger.

- First tests of the LP deck: motor works and runs smoothly. A bit of a hiccup with the auto- shutoff not catching, but some Li-grease and a spring adjustment later, and all is well. Can't test cartridge yet, as the tone-arm hinge was broken. The epoxy is now curing. There's not much stress at that point, so it should hold.

- Working on a restore log... watch for it soon :)

Okay... two birds with one stone.
Here's the build log so far. There is a picture of the frayed coil as the last item on the page; you can click any of the images for a larger version.

Enjoy!

http://vintagepc.co.nr/site/index.php/stuff/radio/

Also, feel free to leave comments as to what you think of the site's layout/design. I've put some time in to revamping it and I'm happy with the result- simple, clean and elegant.
Hope you like it too!

I like your website with the built-in links and all. That coil got lunched, didn't it? Hard to tell but if it was just the outer wires, I'd make a careful drawing of the orientation of the coil in the set and where all the wires go, unsolder it, take it out, and try to scope which broken wires go with which ones. But this coil "looks" like it's beyond that.

One thing you could try, then, would be to carefully unwind the broken turns of the coil, keeping the wire, until you get to just one wire coming out of the good part of the coil. Then carefully scrape to bright copper and solder that wire to the broken pieces one after the other and wind back on as neatly as possible. It's important to wind in the same direction as the coil was originally wound. You won't be able to wind like the machine but that's OK. Have a candle going nearby and drip wax on the coil as required to keep it together. Reassemble and it might work. It might require the tuning cap trimmers readjusted to get it to track.

Another fix would be an oscillator coil out of a junked plastic table radio. Someone on the forum might have a junker that he could send you the coil from: I don't have one at present or I would.

If not, AES sells replacement oscillator coils. I don't know which of these would work in your set, but they're cheap and one of them would: I'd get both and tack them in and try them. Search "oscillator coil:" see the first two $1.95 coils on the page.

http://www.tubesandmore.com/

Thanks- glad you like it!
I wonder if it was the mice, or whether it was something else; there aren't any bite marks in the wax, so it looks more like careless handling or a scrape against a sharp edge.

I'll give the repair a try and see what happens. I think it looks worse than it is because of all the fluff that is present. If not, I may have a spare coil from a junked stereo set I can use- I've amassed quite the pile of spares over a few years; all manner of toroids, transformers, and so forth. We'll see what happens- Thanks for the link to AES.

There are two coils on the same core there... I take it one is for the oscillator, and the other is a "hum-bucking" coil?

Regarding the trimmer adjustment, what would that entail? I don't have extensive sophisticated tools on hand.

The oscillator coil consists of the whole L2 assembly, the two windings together.
Adjusting the trimmer is explained in the instructions with the schematic, but it
all boils down to a simple thing: making sure the stations are at the correct
frequencies on the dial.

By the way, it might be time to give the amplifier a try, feeding it with the line
output of a CD player or mp3 player. Adapters with RCA plugs that fit the
phono input are quite easily found. Bye for now.

Not to worry, I have plenty of RCA-outputting hardware at my disposal, not to mention some R2Rs :)

I've been holding off on ordering the caps etc. because I'm going to be very busy for the next three weeks- no time for projects such as this. (Hence I started with something simple like the turntable). After that, I should have plenty of free time to get in to my own projects, and then this will take off :) Thus, the original caps are still in place, and it's not quite ready for a bench-test yet...

The epoxy should be cured (>24h) by tonight, so I'm going to grab a test (read: not particularly important) 78 and take it out for a spin.

As electroking noted, both the coils shown as L2 are on that assembly, and the two lower ("cold") ends of the coils are connected together and to system ground. If substituting a different coil, determine the common terminal and connect the same as before. If the set won't oscillate (as determined by the set tuning broadly, maybe one station all over the dial), reverse the connections of one of the coils.

Main tuning cap alignment: tune in a station of known frequency near 1400 Khz. The trimmer on the smaller section of the tuning cap will move the station up or down the dial until it reads correctly on the dial scale. Then tune to a weak station around 1400 and peak reception with the trimmer on the larger section of the tuning cap.

Hello again,

The reason I suggested trying out the amplifier was to help you find something
stimulating to pursue the project: the amplifier will work even if the radio section
is not fixed. As long as the function switch is set to phono or stereo, the radio
section is not powered (except for the tube heaters). If you have to set this
project aside for sometime, I would suggest that you do some reading on the
principles of superheterodyne receivers (that just means a receiver with a
local oscillator and demodulation at a fixed carrier frequency called the Intermediate
Frequency). Examples of useful books include any old edition of the ARRL handbook,
good old textbooks such as the one by Terman (Electronic and Radio Engineering),
etc. Bye for now.

P.S.: testing with the turntable and an old 78 is fine too!

Well... game over for now :tears: The TC8S is indeed quite dead... there was crystal dust everywhere.

Looks like I'm on the hunt for a new cartridge. Any recommendations for a drop-in ceramic replacement (TC12H?) or how much I can expect to spend? (and possibly a good supplier in NL?)

Thanks!

Canadian Astatic. Send them your set model number, and all the numbers on your cartridge. They will have one that will work.

http://www.canadianastatic.com/

I've sent them an email and am waiting for a reply.

While googling, I came across this:

http://www.angelfire.com/electronic2...ge-rebuild.htm

Anyone tried it before? Or will that hack only work well in a mono cartridge?
I have several piezo buzzers I've salvaged... and it's not as though they are expensive. Perhaps I'll give it a shot.

I would say don't bother with that, a good replacement cartridge should not
be that hard to find, and it will come with brand new styli. By the way
I looked at your site (thanks for the credit to me regarding the schematic!)
and I wonder why you concluded that the oscillator coil was shot.
Maybe it's obvious to you, but did you trace the connections to the
rest of the circuit to confirm that something was wrong? Good luck.

You're welcome- when the writeup is finished, anyone here who's contributed significantly will be credited :yes:

I figured as much... I'll have a look around to see what I can find locally in addition to AES; chances are a specialty electronics shop may have something.

Re Coil: There are several broken wires coming off the side (click the picture for a larger version, easier to see) and there is no continuity if I test the lower coil with a DMM.

I'm going to give Reece's suggestion a try as soon as I can get back to the project- I think it may be fixable with some care... it looks worse than it is.

Okay... Just in time :)
I dropped by a specialty electronics store and I managed to get his last ceramic pick-up for a good price.

I never heard back from Canadian Astatic, and the cost was less than they asked anyway.

So now I have a Philips GP-815, and I just have to figure out a way to mount it (which shouldn't be difficult- it comes with a small metal plate to clamp it securely; If I drill and tap the plate then I should be able to use the original mounting screw in the BSR tone arm.

Does anyone have detailed specs? All I can find is this page, which offers little help (except confirming that it is ceramic):
http://www.topkaufmunich.de/plaintex...temphilips.php

I would assume the standard tracking weight of around 6g would apply.

(Though I've heard it's better to be on the higher end of the range- which would be ~8g. I know too light will damage the record as the stylus skates around, but what sort of problems would you get with too much tracking weight?)

ok i can't imagine where you scored a ceramic cartridge in our city...i don't do vinyl,but i'm thinking it might be useful to know what business around here even sorta carries stuff like that...best guess's? Hamblins?maybe Peak?

Sorry, it's not in Canada, actually :)
This is in Europe- I've found the newer American Philips (Magnavox?) products to be nothing but crap, whereas here it's still decent quality and a respected brand.

As an FYI, the store is Technica B.V. in Nijmegen, NL.
They would probably still have some tubes on a back shelf or know where to get them, but I didn't think to ask (and trying to transport them by plane is asking for it!)- This guy is basically your local electronics shop for the hobbyist, all kinds of components and supplies.

Edit: I'd wager a store like that would do really well for the tinkerer in Halifax.. but you might try RAE electronics in Burnside. I usually order all my other stuff from Digi-Key, but if you'd like, I can ask around as I know a few people who support older electronics and might know where to get the stuff locally.

oh ok,you referred to me as "a fellow Haligonian" in another thread,so i assumed you were local to me,...but you're living away perhaps?...i figured if you had found a place here that actually stocked a ceramic cart...that was a place i should know about!!

i haven't been into RAE in several years,it was usually a wasted stop unfortunately.they always seemed to put more emphasis on commercial/industrial concerns..alltho welcome,they're not really there for the individual in need of a few bucks in parts was always my impression...Jentronics also in Burnside is my store of choice these days...never had a bad experience,friendly,happy to offer advice and usually have what i need,or will order it in if not...found out on my last trip in that the guy on the counter also had experience in restoring radios...very helpful

Ordinarily, yes, but I'm visiting family at the moment :thmbsp:

II've heard of Jentronics, and I'll have to give them a look sometime.

Another decent place is Princess Auto; while they have mostly tools and car parts, they have miscellaneous electronics in the surplus section... great place for AC adapters and cheap cables, fans, etc- While I doubt they carry pickups, it couldn't hurt to give them a call.

I wonder if Halifax is just too small to support such a store- the major problem being supply. It seems to me that this "old" technology is just much more alive in Europe than in the Americas. (e.g. the video about the man making his own triodes- he's in France)

*Hisssss* *crackle* bada-BUMP! :D
 

Okay, I'm back at it :).

Just for kicks, I asked the guy if he also had any dial cord or tubes... Negative on both counts, but I did win that bet :D

Anyway, I was able to mount the new cartridge, wire it up and set the tracking weight using a jury-rigged balance and a loonie (which is exactly 6g!).

However, doing a dry run, (nothing connected to the turntable), I can actually hear the sound on the record. It's not loud, and somewhat tinny (kind of like someone standing next to you with their earbuds cranked.)

The needle isn't skating, it is well seated in the groove.

I don't want to damage anything, so I stopped right away... More newbie questions:

- Is that normal, or too much/little tracking force?

-If not, could it be the stylus angle (and should it be 90 bang on, or more/less)?

Finally, I still have the TC8G and TC8S styli... Both look in good shape. Anyone want to buy them to fund my restoration? :scratch2: "Super macro" pics on request.

Many ceramic cartridges produce an audible acoustic signal if you bring your
ear close enough, no need to worry. Good to hear of you again!

Well, in that case, the turntable now works!

Back to the chassis... The oscillator got lunched all right. It's well beyond repair.... Off to source a replacement :)

Would it be an idea to re-build the coil? I've calculated the length of damaged wire to be 5m, and I have the same fine stuff on hand.

Could it work, or would the new specs be different enough to require adjusting the set anyway? (what I'm hoping to avoid)

It will require alignment of the trimmer on the oscillator section of
the variable capacitor, but that's no big deal. IF
alignment (the slugs in the IF transformers) should not be affected.
Rebuilding the coil on its original cardboard core will probably
yield better results than trying to fit a 'universal' replacement coil.
By the way, the exact number of turns matters more than the length
of wire, so try to stay as close to original specs as you can. Also the
wire must be enameled (thin coat of varnish rather than bare wire
or wire with plastic insulation). This is often sold as 'magnet wire'.
Good luck!

Unfortunately the coil was so chewed up I couldn't reliably count the number of turns.

However, I did piece all the lengths together and I would assume that with the same total length of wire, wound in the same manner (or as close as possible) would result in the same number of turns.

I have numerous low voltage transformers that I'm never going to use for anything else- I'd thought to salvage the wire from one of those, provided it's not potted. I also have a huge copper coil (magnet wire) from a TV yoke, but I think that's too thick to use. Fortunately, the secondary coil was untouched, and so I have it for both a reference in wire size and winding pattern.

Looks like you did your best to gather all the available info. It's time to start
experimenting! As long as you get the correct phasing (relative polarity of
the two coils), it should oscillate. Personal message to follow within one day,
bye for now.

Yep... We'll see how it goes.

I'm waiting for a nice sunny (and insect-free) day so I can finish derusting the chassis and power transformer casing, and I hope to get in an order for some replacement capacitors once I've tested for out-of-spec resistors.

Thanks for all your help!

Just finished re-winding the coil (pic below) and I'm waiting for the wax to harden. The CRT yoke had perfectly salvageable wire (and more than enough on just one winding- I nearly filled an 800 yard thread spool!

I reinstalled the coil and looked at the circuit diagram- it seems that there are some differences- (or someone has already "serviced" the radio.

Particularly, C25 and C26 are 0.01 µF (vs .03) and one of the filter caps in the can is 100 µF as opposed to 40 on the schematic.

R5 and R31 are completely absent.

Regarding replacements, I take it aluminum caps are fine for the electrolytics, and ceramics to replace the plastic and paper ones?

Also, can someone confirm whether C12,22,16, and 17 are electrolytic? They have the same schematic symbol as the filter caps, but like kinda like the plastic jobbies. (or just leave them alone?)

>Particularly, C25 and C26 are 0.01 µF (vs .03) and one of the filter caps in
>the can is 100 µF as opposed to 40 on the schematic.

Those 2 capacitors bypass the power line to the chassis to filter out some
interference. They are sometimes called 'death caps', because while
they are useful for their stated purpose, they also increase the leakage
between the power line and chassis, and bring up some shock hazard.
The lower value is possibly a production change, you need not worry,
but make sure good capacitors are in those spots. The 100 µF can
is probably fine for C23, but at C24 it may overstress the rectifier tube.
Better limit this one to 40 or 50 µF.

>R5 and R31 are completely absent.

Maybe they were removed by someone who wanted to disable the
radio section; these resistors provide the proper voltage and current
to tubes 6BE6 and 6DC8. The node between R3 and C5 should
definitely not be connected directly to the function switch, or the
tubes may be overloaded. You could replace R5 and R31 by a single
10 kohm, 3 to 5 W resistor. (note added afterwards: maybe the
resistors were moved to the part of the supply line on the other
side of the switch, somewhere to the right of C11)

>Regarding replacements, I take it aluminum caps are fine for the
>electrolytics, and ceramics to replace the plastic and paper ones?

Well electrolytics and aluminum electrolytics are essentially the same
(although there are also tantalum electrolytics, not very often used
in tube gear). Ceramic capacitors don't usually come in large values
(0.1 microF) and reasonably high voltage ratings. But in this radio,
probably anything with correct voltage and capacitance rating will do.

>Also, can someone confirm whether C12,22,16, and 17 are electrolytic?
>They have the same schematic symbol as the filter caps, but like kinda like
>the plastic jobbies. (or just leave them alone?)

Those cathode bypass capacitors are definitely electrolytic, but they
are low voltage units, that is why they are smaller. 6- to 15- volt
units would be fine for C12/C22, and 25-V units for C16/C17. You
can read the cathode voltages on the schematic, respectively 1.1 and
12 volts. These should be replaced, as any leakage will screw up
the bias on the tubes. P.S.: modern plastic units for C12/C22 would
be fine if not too physically big; some audiophiles will even tell you they
will improve the sound!

Good night.

The 100 µF can is indeed C23, so I'll see what I can get and may change it for a 40 if circumstances require.

I'll also look in to good replacements for the death caps; chassis ground is also turntable ground, so it is a big issue.

It turns out that R31 and R5 are present after all; they are before the function switch and tucked away, so I did not see them until I searched thoroughly.

I'm placing an order with Digi-key for other electronics supplies, so I'll get as many of the caps as I can there... if all goes well, I may be able to do a preliminary test next week! *crosses fingers*

Not much other radio progress, but after an afternoon with some steel wool and rust remover, I think I've eliminated all the rust. The line cord has also been replaced (the prongs on the old one were bent up and corroded.)

Death caps, leakage to chassis, etc.
 

Hello again,

Regarding the death caps and shock hazards, it might be a good idea to
install a polarized plug (maybe cannibalized from a dead TV) with the
neutral (wide blade) connected to the lower side of the power
transformer and the live (narrow blade) connected to the upper
side (the one with the power switch). This would ensure that the
resistive link to the chassis (R55) would remain on the neutral side
of the line. R55 is part of the filter along with the death caps.

I found the polarized line cord I had; and installed it.

I'm currently re-painting the transformer case and have removed the filter cap can (and gutted it) for re-stuffing.

Capacitors have been ordered and are on the way!

There's a bit of a lull in activity now, since I'm waiting for my caps to arrive. More photos have been posted and updates made to the restore log on my site.

http://vintagepc.co.nr/site/index.php/stuff/radio/

Hope it tides everyone over!

*Twiddle Twiddle*
 

Still twiddling my thumbs. I'd hoped the caps would arrive today, but probably will on Monday (because of the holiday Thursday).

Can't do much else until I have those, but I did rig up an external RCA input using a dual-pole dual-throw switch and some RCA jacks, plugs, and shielded audio cable... so when the set is done, I'll be able to switch between the internal turntable and an external source at the push of a button!

The only issue I could see is with the set's floating ground- Would it cause an issue if I plugged in an audio source with a hard-wired ground?

Anyway, once I've recapped, what would be the best way to power up the set? I don't have a variac (alas) but I'd thought to pull all the tubes, check the transformer output voltages, and then put the tubes back in one by one, testing voltages (indicated on the schematic) as I go.

No problem with ground floating ground, it will just cease to be floating
when connected to a grounded source. This is not really a hot chassis,
the power transformer does provide isolation. You can ground the chassis
to earth if you make sure you have the correct power line polarity as
discussed before, end even with incorrect polarity, the leakage will
be small and tolerable as long as the line filter components (one
resistor and two capacitors) are OK.

Do not plug the tubes one by one! Instead, install all the tubes
except the rectifier. It would be best to start up with a variac
(do a bit of research with this word), or with an incandescent
bulb in series, but in a pinch the line fuse will do. With power
applied, tube heaters should light up (not very bright, but visible
in the dark). Let the set run (while watching) for maybe 30 minutes.
The power transformer should get mildly warm, but not any hotter.
Without rectifier, no DC will be generated, so no voltage measurements
to be done at this point.

You may use your old tubes for this test (hope you did not discard
them), many or all are likely to be good. Bad tubes would be
detected later by measurements and substitutions.

Now with power off, install the rectifier tube. The time for the
full test is approaching. Securely hook up your DC voltmeter to C23 and
ground. Turn on power, and watch the meter. The situation
is now the same as before, so no sparks are expected, but as
the rectifier warms up, the correct DC voltage (275) should appear.
If the value is substantially lower, it means you have a short somewhere
down the road from the rectifier, HIT THE POWER SWITCH. Otherwise,
listen for some hum in the speaker, etc. You may start doing the
voltage measurements you suggested.

This should get you going for a while. Good night.

Yes, I did keep the tubes that were in there :) I'm not tossing anything until I know for sure it's bad.

Regarding the variac... I might be able to borrow one from work... I'll have to ask. If not, then I should have enough stuff to make a dim-bulb tester.

Good news- I've sourced a variac that I can borrow.

With this, I've read that the procedure is to bring the set up in steps (typically 10v steps/30 min?) Can someone confirm or provide a link to a good guide for doing this? I've found a few, but those all discuss re-forming the original filter caps and precautions if you're bringing the set up with the original paper caps- I'll have replaced all of those by then, so I don't know if the process differs much.

There's also something about a point around 40-50V where things get near the minimum operating voltage to run, and that it should be left there for longer.

Thanks!

Re-forming applies to the power supply electrolytics. If they are new and
correctly wired, there should be no problem with those capacitors.

Without the rectifier, you can turn up the variac as slowly as you wish, but
when you do the test with the rectifier in place, dont run the unit under
say 80% of nominal voltage for more than a few minutes. If it seems
to be idling OK at 80%, you can get it up to 100%. This radio is much simpler
than a TV, where for instance lack of horizontal drive could fry the sweep tube.

Also, in addition to what I wrote to you last time, you should do the initial testing
with rectifier with the function switch in PHONO or STEREO, rather than
RADIO (or BC). This will keep the two radio tubes off the high voltage.
Of course, this test should be done with the speakers (or load resistors) connected.
After checking the high voltage at C23, the next measurements should be
the cathode voltage at the output tubes (pin 2 of each 6AQ5, 12 volts) and
at each of the driver tubes (pin 7 of each 6AU6, 1.1 volts). Correct values
at these four points will almost certainly guarantee that the tubes are correctly
biased.

Once you get the audio section working, we'll have a look at the radio part.
Good luck.

Thanks for the info- good thing I asked too- since sometimes being to cautious is just as dangerous as not.

My capacitors arrived today... So I'm going to have me a restuffing party!