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 Post subject: Re: Westinghouse H-693P8 project...
PostPosted: Oct Sat 17, 2015 9:38 am 
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Nice work John, looks damn near brand new! I think your sub of the audio output Transistors had a large effect on it's performance.

I had accidentally broken one of the audio output Transistors on one of my Tom Thumb hybrids, and subbed a more recent Transistor in it's place, and it screams. Far more -apparent sensitivity- and volume than my other "stock" models.

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 Post subject: Re: Westinghouse H-693P8 project...
PostPosted: Oct Sat 17, 2015 4:11 pm 
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Thanks Richard !

The replacement audio transistors did correct the distortion when I replaced them, but the volume was about the same as before even though you could hear more stations in the background noise.

The huge improvement in performance came after removing speaker sub-chassis---then re-positioning those transistors whose cases were touching speaker frame. That also completely eliminated that intermittent mid-band squealing/oscillation---think that there was just enough coupling of the mixer transistor signal to the IF transistor which was also touching to cause both problems. Have thought of using test leads to recreate the problem, but not enough time or motivation right now. Even though the cases of transistors are "isolated" from the elements, there is probably enough "case to element" capacitance to cause these bizarre "issues"---didn't check for leakage to cases (tin whiskers), maybe that needs to be added to list !

Am listening right now to my favorite distant, low-power station---sound is fine for such a small set, not "tinny" as I mentioned earlier, just typical for a small set of that era... Very impressive little radio !

How tight are your tuning shafts ? Have you tried lubrication ? Just wondered as that's next on list for this set since it's so difficult to tune !

John


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 Post subject: Re: Westinghouse H-693P8 project...
PostPosted: Oct Sat 17, 2015 7:09 pm 
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The only thing I can think of for better fine tuning is either a cap in the right place to slow the tuning rate or a larger dia tuning knob. Also, perhaps a BAT35 is in order?


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 Post subject: Re: Westinghouse H-693P8 project...
PostPosted: Oct Sat 17, 2015 8:35 pm 
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Nice work John! Perhaps I should try adjusting the alignment and seeing if any transistors are touching the shield on my set (although mine does not have any oscillation issues). I did oil both the bearing race and the single bearing at the bottom of the cap, which did not improve it much, I think the frame is just too tight on the bearings (I did not want to risk trying to loosen it).

I have not seen reject transistors in radios by any of the major brands, but some off brand American sets did use them, such as sets by Futura or Bell Products (both company's products are very poor performers).


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 Post subject: Re: Westinghouse H-693P8 project...
PostPosted: Oct Sun 18, 2015 4:07 am 
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Location: Indianapolis, IN
Thanks Guys !

db gain---Thought of making a temporary mount for an external vernier drive unit I have in "junkbox" which could be attached without harming radio. This set has a transistor for detector & performance is excellent as it is, so don't plan any internal mods. Also thought of using a large tuning knob from "knob drawer" just for fun and may do so...

Matt---thanks much for the tuning cap "lube report" ! Now I know not to go through the trouble... Have other sets that lubing didn't help, so will add this to list. When you have the frame off, attach clip lead from it to PCB ground (to complete speaker circuit) and see if you notice improvement. And the IF's should peak nicely if working---if adjustment makes little difference, perhaps internal connection has failed as mine did intermittently prior to the re-soldering mentioned earlier... Still think the transistors with clipped off leads is odd---maybe not total rejects, but just not "up to snuff" for intended use by T.I. ?

John


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 Post subject: Re: Westinghouse H-693P8 project...
PostPosted: Oct Sun 18, 2015 9:43 am 
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xrhonda91 wrote:
Still think the transistors with clipped off leads is odd---maybe not total rejects, but just not "up to snuff" for intended use by T.I. ?

John

I don't think so, John. In the first place, you say that the set now works as well as some with an RF stage
Quote:
This radio now does as well as some of my tuned-RF amp equipped sets with excellent selectivity.

which would hardly indicate sub-standard active elements.

Additionally, I've noticed some early oval shaped Transistors in my stash that also have a clipped 4th lead, so I wasn't at all surprised when you reported that your set had them. I've never really concerned myself with what they were for, so can't offer any explanation.

Just glad to see that you have restored a mediocre appearing dead set, to a looker that apparently performs as well as it looks. :D

Richard

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 Post subject: Re: Westinghouse H-693P8 project...
PostPosted: Oct Sun 18, 2015 3:53 pm 
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It just so happens that I have an old TI transistor with a clipped off 4th lead which has lost its top (the case was so corroded that the lid fell off when I tried to remove it from the socket).
Here are some close up shots of said transistor. Notice something odd in the last photo?


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 Post subject: Re: Westinghouse H-693P8 project...
PostPosted: Oct Sun 18, 2015 5:29 pm 
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Wow Matt, those are great pics---thanks for posting !

Do you still have my e-mail address to send the hi-res files ?

The internal construction sure looks "crude". The 4th pin is another "base" connection as I thought after taking resistance measurements---maybe this was done in case the assembler reversed the emitter & collector connections ?

Is the fly a spy ???

Well Richard---the radio does perform excellent now, but you know how tight military specs are and if these T.I. transistors were intended for military use and fell just outside their limits, they still could do very well in a "civilian" radio. Would sure be interesting to talk to an old Westinghouse engineer ! Guess the slight difference in base construction and the numbering aroused my suspicions...

John


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 Post subject: Re: Westinghouse H-693P8 project...
PostPosted: Oct Sun 18, 2015 6:27 pm 
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Those pictures are as high-res as it gets unfortunately, I just cropped the original photos down to the size limit.

I agree, I think it was setup such that the "incorrect" base connection could be clipped off leaving the leads in the correct order. These early transistors were completely hand assembled, and I bet it was not easy to do. Many but seemingly not all early TI transistors have that 4th connection and I am not sure why only some were made that way.

When I took this transistor out of my little display, I noticed there was a tiny fly stuck to the (silicone?) grease on the transistor, so I took a picture before removing it.


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 Post subject: Re: Westinghouse H-693P8 project...
PostPosted: Oct Sun 18, 2015 6:40 pm 
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Hey Matt,

I saved those images since they're so good... A fly in the silicone "ointment"---hmmm... Wonder if egg was in the transistor since the 1950's ??? Joshing of course...

This is the first time I've noticed the 4th lead---will be on the lookout now...

Thanks again for the pics.

John


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 Post subject: Re: Westinghouse H-693P8 project...
PostPosted: Oct Sun 18, 2015 8:10 pm 
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Nice pics there, wondered what they looked like inside.

Also, wonder if the transistor used as a detector isn't the reason for the radios stellar performance?


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 Post subject: Re: Westinghouse H-693P8 project...
PostPosted: Oct Mon 19, 2015 2:37 am 
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db gain---imagine the transistor as detector does make a noticeable difference. That long, wide ferrite bar sure doesn't hurt !

John


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 Post subject: Re: Westinghouse H-693P8 project...
PostPosted: Oct Mon 19, 2015 5:28 pm 
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Joined: Aug Fri 29, 2014 6:17 pm
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On the tuning issue, if you make it easier to turn by grease on the bearings or whatever you'll zip right past where you want to listen, with a fast tuning cap you want it to offer a bit of resistance.


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 Post subject: Re: Westinghouse H-693P8 project...
PostPosted: Oct Tue 20, 2015 2:36 am 
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Hello db gain,

This tuning cap is much tighter than normal and Matt said that lubing his made little difference. If it was screwed to PCB, I would give it the full acetone and re-lube "treatment" which freed up a couple others I had, but it has heavy tabs which are soldered and don't want to destroy the circuit board trying to remove it...

John


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 Post subject: Re: Westinghouse H-693P8 project...
PostPosted: Sep Tue 14, 2021 12:47 am 
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Location: Indianapolis, IN
Hello All,

I picked up a $10 Westinghouse H-653P6 6-transistor set for a friend from same seller I purchased a maroon Zenith Royal 500A recently. Was amazed that it worked very well other than "scratchy" volume & tuning controls when I connected battery with test leads---with original tubular ceramic Nashville electrolytics ! Since it was such a good performer, decided to pull this H-693P8 off of shelf for comparison. It had been years since I last listened to it and the "acetate fungus" was returning to the knobs which surprised me since the H-653P6 knobs were still clear ! Installed battery and now completely dead---not even a "click" from speaker !!! Took some quick measurements and discovered that the speaker was now open---arrgghhh !!! Going to pull it apart and see if perhaps the open is at one of the terminals (hopefully !) There was absolutely no battery leakage residue in this set to corrode the voice-coil flex-leads, so maybe it'll be repairable...

John


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