[Nadanutcase]

Hello everyone. I've been engaged in antique radio restoration for many years but I'm new to this forum.

I bought a 38-690 at an auction a couple years ago and have started to go through it. The power transformer that supplies the audio output stage has shorted (smoked) windings. According to the parts list (and per the markings on it) this is Philco part number 32-7887 (for 115 / 230 Vac, jumper selectable). But there's also a part number 32-7885 that is used in 115 Vac sets only.

Can anyone tell me if these were used in other models? Does anyone have a useable one? Or are they as uncommon as the 38-690 and I'm up a creek?

Thanks for any information.

Dave

[Ron Ramirez]

Hi

I've never heard of a 38-690 that had 115/230 power transformers. Very unusual.

Because of that, I would say your chances of finding another 32-7887 are, frankly, slim to none.

You might even have a hard time coming up with a 32-7885.

There is a good alternative, however: Have Heyboer Transformers in Michigan custom wind a new transformer for you, to the same specs as the original 32-7887. If you work closely with them by providing as many details as possible, you can use the original cover and end up with a brand new transformer that is just like the original in every aspect.

http://www.heyboertransformers.com/

They provide excellent products. I've had three or four custom wound power transformers made by them for sets I was restoring when I used to do radio repair as a sideline - never a problem with any of them. They are not cheap, but are surprisingly reasonable considering a new transformer built to original specs is a one-off special order job.

A set like a 38-690 is well worth the extra effort and expense...in my opinion.

[Nadanutcase]

Thanks, I was hoping that, if nothing else, there'd be an option like that.

Both of the power transformers in this set have an octal jumper plug that can but rotated to use either 115 or 230. The two transformer options are listed on the parts list, but the schematic doesn't show the jumper, just a single primary. The other thing I found, just on this transformer, is that someone had replaced the recifier socket and it's not wired correctly for a 5X4. Maybe they wanted to use a 5U4? Don't know.

You're right, this set is in great physical condition otherwise and well worth some expense. Have you got even a ballpark guess as to what they'd charge if I sent them the original & a schematic with the specs?

[Ron Ramirez]

Every transformer Heyboer wound for me cost around $100-125. Yours will probably cost around $100-150, I would guess. A fair amount of $$ but again, the 38-690 is worth fixing up the right way. And having a custom wound 115/230 transformer would allow your set to retain its original appearance and specs.

Remember, you will have to reuse the top portion of your original transformer (tube socket, voltage change jumper plug and socket, top cover). You will have to be sure Heyboer makes the transformer so it is the same size as the original, and that the wires come out on the same sides as the original.

[Nadanutcase]

I'd say this set is well worth that. Over the years I've encountered relatively few problems with transformers and inductors (aside from open inter-stage transformers in some of the earliest sets) and generally when I've found one, the set's value would not warrant the expense of a custom part so I'd either design a work-around and hide it as best I could, or relegate the set to "parts". I think I'll have them wind it with just a simple, single primary for 115V then mount the jumper & rectifier bracket on it so it looks like the original even though the jumper isn't functional.

I haven't poked around this forrm enough to know how / where to post a picture. I can post one of the chassis and the transformer(s) if you're curious.

[Ron Ramirez]

Not a bad idea, having a new one built with only a 115 volt primary, but keeping the hardware for appearance's sake.

I forgot to mention, on every transformer I had Heyboer wind for me, I asked for a 130 volt primary, to compensate for today's higher line voltages of 125+ volts.

The line voltage where I live stays pretty steady at 125. When I lived in Evansville, it would often go as high as 128.

The "how do I post a picture" question gets asked a lot...enough that I wrote up a couple tutorials on the process which may be found in the "Phorum 101" section which most people miss because you have to scroll all the way down to the bottom of the home page to find it. Hmmm...maybe I should move it to the top of the home page...

http://www.philcoradio.com/phorum/forumd...php?fid=27

Overview: How to Add Images to Your Posts
http://www.philcoradio.com/phorum/showthread.php?tid=29

Phorum How-To #1: Add Photos To Your Posts using Photobucket
http://www.philcoradio.com/phorum/showth...p?tid=4371

[Arran]

There a a few outfits that will rewind transformers, Heyboer is one, I have also heard of an outfit in Ohio (I can't recall the name) and a fellow in Maine that also offer satisfactory service. One thing you should ask about is if it would help cut the cost in any way if you sent a stripped core to them, I don't know if they need that portion or not but I'm sure that they have to pay someone to remove the old windings. One nice thing about modern materials is that they could likely rewind a transformer with higher current rating then the original on the same size core, if including an extra tap on the primary for 240 volt line operation doesn't cost too much more I would have that included.
Regards
Arran

[Nadanutcase]

OK - thanks for the feedback so far. I have contacted Heyboer to get started on a replacement transformer.

Meanwhile, it seems that the transformers in this set are somewhat unusual in that they have a jumper to select 115 or 230 V operation, so for anyone who is curious, I've posted a few pictures.
First here's the chassis in the radio:

http://i791.photobucket.com/albums/yy193...49cdec.jpg

Here's the part number (again - this does show as an option on the parts list, but the schematic I have doesn't reflect the jumper option):

http://i791.photobucket.com/albums/yy193...9eb051.jpg

Here is the voltage programming jumper. You have to remove the cover to see that it's an octal plug that can be rotated to select the input voltage:

http://i791.photobucket.com/albums/yy193...ad65ab.jpg

And, finally, here's a shot of the cripsy leads and a rectifier socket that has been replaced AND that's not wired correctely for the original 5X4 rectifer:

http://i791.photobucket.com/albums/yy193...b16b7a.jpg

I have no history on this set. Here is my best GUESS as to why it was set up for dual voltage operation: Our club (the Iowa Antique Radio Club and Historical Society - http://www.iowa-antique-radio-club.com) holds an auction each Spring that draws people from around the midwest, including some regulars from Minnesota. A couple years ago one of them brought this set to the auction and I bought it. I have no way to know, so I'm guessing that this set may have been originally sold near or in Canada where 230 volts line voltage was in use.

Does this forum include anyone from the Maple Leaf country that can shed any more light on that ??

Dave

[Ron Ramirez]

Canada was, and is still, on the 115 volt line standard. Although, their line voltage may have moved up to 120-125 by now as ours has.

For what it's worth, I have a 37-670 with a power transformer similar to the two in your 690 - that is, with the covers and the 115/230 switchable jumper.

We probably won't ever know the reason why, but it looks like Philco built some domestic sets in that time period with the 115/230 power transformers.

Also, if your set was built in Canada, it would have a metal tag on the back of at least the top chassis stating that fact along with the model number. I have a listing of Philco radios built in Canada before WWII, and I don't believe the 38-690 was made or sold in Canada - I think the 38-C116 (Canadian equivalent of the USA 38-116) was their top of the line set. Arran? Any thoughts on this?

[Arran]

They build and sold 16/116 series sets for the Canadian market most definitely, I don't know about the 690 sets, they may have imported those if they sold them here at all, or at least the chassis. I don't know where this idea of 230/240 AC mains being ever used in Canada came from because it is 100% false. 115 volt AC mains was used in some areas, usually at 25 cycles per second line frequency, most areas with 60 cycle power were the same as the U.S and the line voltage could vary between 105 to 125 volts depending on the local service and time of day.
Canada being a relatively small country it would never have made sense to use an entirely different power system from the U.S, it would have increased costs to no real advantage. In fact during the late 1950s they started ripping out the 25 cycle power grids in part because of this, I think the last 25 cycle service still offered was to some steel mills in the Hamilton area of Ontario back in the 80s. Now the line voltage is 120 volt at 60 cps pretty much everywhere, here it seems to be pretty constant give or take a volt.
If this was a Canadian market set, even if it was imported they still would have added that brass tag on one of the chassis with the model, line voltages, and the serial number, sometimes with fine print about being built under license of Canadian Radio Patents LTD. The set would also have a round decal with a crown logo someplace proclaiming that it was approved by the Hydro Electric Power Commission of Ontario, this was in the era before the Canadian Standards Association labs got rolling.
Regards
Arran

[Nadanutcase]

OK, the Canadian tie in was just a wild guess on my part as to why it has the 230 V option. There is not brass plaque on the back. I did note on the parts list that there was also a 25 Hz transformer option.

ON TO ANOTHER REQUEST REGARDING THIS TRANSFORMER: I've made contact with the Heyboer and removed the transformer from the chassis (taking pictures all the way). The secondary is intact; it ohms out pretty much per-spec as shown on the schematic and it's the primary that smoked. Here's the relevant section of the schematic:

http://i791.photobucket.com/albums/yy193...2a9c3.jpeg

I'm trying to work out what specification I should give Heyboer for the input / output voltage. I think 120Vac for a single primary is reasonable (I've elected to forego the unneeded complication of routing the leads for a dual voltage primary to the top side of the transformer since I'll never use them, and just mount the jumper there for appearence sake). So that leaves the O.C. secondary voltage specification. Starting with a "typical" working plate voltage for the 6L6 output tubes in push-pull and working backwards through the filter components & rectifier. I came up with about 600 Vac (RMS) (300 V from the end to the center tap of the secondary). But to sanity check myself I took a look at the power supply design section of an old radio handbook from that era and the general formulas in there point to just under 500 Vac (250 V end to center tap) as the target secondary voltage for a supply with a capacitive input filter. I don't have anything in my reference material for this set that says what the typical operating values are in circuit. It would be just GREAT if someone who has 38-690 happens to have that information. Lacking that, I open to suggestions.

Under the heading of FWIW, in case you're wondering who you're chatting with, I also uploaded a photo of me taken a few years ago when there was a bit more hair and it wasn't at gray; I think you'll reconginze the little set on the left:

http://i791.photobucket.com/albums/yy193...radios.jpg

[Arran]

Most of the time a dual voltage primary only involves adding an extra lead to the primary, so the primary would have three leads instead of two, and the resistance of the primary would be 5 ohms instead of 2.5 ohms, although it looks like they added more to this transformer. I think that if the 240 volt mains option is eliminated it should be clearly marked someplace that this was changed. I would also recommend having the primary rewound, even if it is single line voltage, to 125 volt specs, if the line voltage goes any higher then that the power company has an equipment problem. One of the information folders available from Chuck Schwark should have more data available regarding the transformers used in this set, I believe there are two.
Regards
Arran

[Nadanutcase]

Sure, I understand how a tapped primary is usually laid out. The reason for my decision, aside from the fact that this set will almost certainly never need to operate a 220V, is that the primary leads (and secondary center tap) enter the transformer below the chassis while the leads to the jumper plug pass through the top along with the leads from the secondary, the recitifer filament and the B+ from the rectifier to the filter, so that adds to the complexity of how the leads are routed inside the transformer and that MAY have contributed to the failure of the transformer. In this picture the bottom socket is the jumper plug:

http://i791.photobucket.com/albums/yy193...b16b7a.jpg

With a simple, single primary, there'd be nothing connected to the jumper socket. In my book, simple is good & more reliable.

Thanks for the lead to Chuck Schwark's file. I am new to this forum, I'll try to figure out how to find it, but I may be back for some tips.