The PHILCO Phorum
Another Update on model 87 restoration - Printable Version

+- The PHILCO Phorum (https://philcoradio.com/phorum)
+-- Forum: Philco Radio Discussions (https://philcoradio.com/phorum/forumdisplay.php?fid=5)
+--- Forum: Philco Electronic Restoration (https://philcoradio.com/phorum/forumdisplay.php?fid=8)
+--- Thread: Another Update on model 87 restoration (/showthread.php?tid=3523)

Pages: 1 2

Another Update on model 87 restoration - wendell - 07-29-2011

Hey Guys,

My tubes came in the mail today. I plugged them in and stared at the power switch knob for quite awhile mustering up the nerve to turn it on, not wanting any bad news. To my surprise it powered right up and after a few seconds I had music coming from my speaker.

All is not perfect, so I have a few more questions:

I'm having a problem with the volume..I have to play with the knobs to get the volume down to a comfortable listening level, it has enough volume to run you out of the room. I'm not sure I understand the controls completely. For any of you that are familiar with this model, there are 4 knobs. Going from left to right, I assume the first is the volume control. To the right of that, the upper control is the tuning control, directly under that is the on/off switch. To the far right, there is a device that looks like a mini variable capacitor, which affects volume, and has a detent if you turn it all the way counter clockwise. What is this control? The control all the way to the left doesnt seem to have any effect on volume.

Any help with this would be appreciated. I think I'm getting close.

Wendell

Re: Another Update on model 87 restoration - Radioroslyn - 07-29-2011

Hi Wendell
Glad to It's up and running!! The knob to the right is the range control. What it is is a small variable cap (like you said) that is in parallel with the main tuning cap for the first rf amp. Now what that should do is give you a small amount tuning to help separate two station that are coming in at the same time.(close in frequency) That's the major drawback with the TRF design is the selectivity is not so good.
If you turn it all the ccw it activates a switch. But for the life of me I can't remember what the heck it does. Sorry.
I can tell you if you hook a jumper from the ANT post to the LOC post and the line cord is plugged in the right way it is suppose to act like an antenna. A poor one but an antenna none the less.
Terry

Re: Another Update on model 87 restoration - Ron Ramirez - 07-29-2011

If you turn the fine tuning or "Range Control" fully CCW until it clicks, it acts as a crude local-distance switch by effectively shorting out one stage of RF amplification.

Re: Another Update on model 87 restoration - Radioroslyn - 07-29-2011

Is that the plus in the neutrodyne plus? It doesn't have a tone control or avc.
Terry

Re: Another Update on model 87 restoration - wendell - 07-29-2011

Thanks again for the replies and help. After letting the set play for awhile and turning the volume control back and forth a few times it seems to be responding a little better now. And the small variable cap does help with fine tuning. I'll clean the volume control when I get a chance and see if that helps further.

I am experiencing a little bit of an annoying hum, like an ac line hum. I may live with that unless you guys can suggest a fairly easy fix for that too.

An interesting thing...there are stickers/labels with the name of the repair shop on the tubes indicating that they were checked in 1932,(apparently put on while servicing the set) and the sticker on one of the 26 tubes lists it as bad. That was 79 years ago and the tube is apparently still kickin.

Wendell

Re: Another Update on model 87 restoration - codefox1 - 07-29-2011

Tube testers wer no better then. If it plays nice, it's good. Hum means weak caps. You did replace them didn;t you?

Re: Another Update on model 87 restoration - wendell - 07-30-2011

Yes, I replaced all the caps. The hum is more like a buzz I guess. Almost like interference,
But right now the spot it's in shouldn't be picking up anything. None of the other radios in the area are picking up anything.

Re: Another Update on model 87 restoration - gvel - 08-01-2011

wendell Wrote:The hum is more like a buzz I guess.

Wendell, my first restoration was a TRF, and it had a buzz too.

Add a line filter cap and see if it helps. If you don't have a "safety cap" handy now, just use a 630 V/.022 uF poly cap. You could also use a .01, .047...or whatever for now.

If you're not familiar with safety caps, look here:

http://www.justradios.com/safetytips.html

Re: Another Update on model 87 restoration - wendell - 08-02-2011

Greg,

Thanks for the reply..where do I install the safety cap? (Specificallywhere? I'm a novice at this stuff.) I have a .022 poly cap on hand. I'll read the article.

Wendell

Re: Another Update on model 87 restoration - Ron Ramirez - 08-02-2011

Most AC/DC radios have one safety cap connected across the line, while most AC-only (those which use a power transformer) sets use two safety caps, each one connected between one side of the line and chassis ground.

Follow the link which Greg (gvel) gave you to the page on the Just Radios site. There is some very good information there.

The first illustration on that page shows how two line-to-ground safety caps are connected in an AC-only radio with a power transformer.

The second illustration shows an across-the-line cap in an AC/DC set.

Philco did not start using line-to-ground caps until the model 111 came out in January 1931. The 87 did not have line-to-ground caps originally, although it certainly won't hurt anything to add them. As the text states, the use of these will help filter out interference in the AC line. Be aware, though, that the use of these will cause the chassis of your 87 to have some AC potential on it. The current, however, is minuscule.

Re: Another Update on model 87 restoration - wendell - 08-02-2011

thanks,

I'll give it a shot.

Wendell

Re: Another Update on model 87 restoration - Radioroslyn - 08-02-2011

>although it certainly won't hurt anything to add them.<

If you like getting shocked if you are grounded and you touch the chassis. But it only hurts a little cause the current is low.
I don't know if it will effect your hum problem. I would suspect that grounding the chassis to a good ground would do the same thing.
Terry

Re: Another Update on model 87 restoration - Radioroslyn - 08-02-2011

Forgot to mention the 87 kinda does have a line bypass cap. It's connected to the LOC terminal. If you ground the LOC terminal it will do the same thing.
Terry

Re: Another Update on model 87 restoration - Ron Ramirez - 08-02-2011

7estatdef Wrote:If you like getting shocked if you are grounded and you touch the chassis. But it only hurts a little cause the current is low.
Read my previous post again, where I said:

Quote:Be aware, though, that the use of these will cause the chassis of your 87 to have some AC potential on it. The current, however, is minuscule.
As for the LOC terminal being used as a line bypass, yes, it could have served this function if the LOC terminal was grounded, and if the AC cord was plugged in so that the hot side of the line was in contact with the other end of the capacitor connected to the LOC terminal.

But this was not the intended purpose of this terminal; it was intended to allow the user to use the AC line as a makeshift antenna by connecting the ANT and LOC terminals together. Again, it would only work if the AC line was plugged in so that the hot side was in contact with that capacitor, the other end of which was connected to the LOC terminal.

Re: Another Update on model 87 restoration - gvel - 08-03-2011

7estatdef Wrote:I don't know if it will effect your hum problem.
Terry

The OP claims, "The hum is more like a buzz I guess." The addition of a single line to ground filter - could eliminate this "buzz". No harm trying, it's only a 10 min. job.