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Old 21st Jan 2021, 7:28 pm   #1
daveoverride
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Default 1965 Mustang AM radio restoration. 5TMZ.

Hi guys,

After buying cleaning and polishing this radio I have plugged it to 12V added a speaker and all it did was slowly smoke. I removed the cover and determined that there was no obvious damage to electrical and mechanical components. I plugged the radio once more and observed that the smoke was coming from this transformer. Out of curiosity I took it apart (I was looking for charred plastics or burnt wiring) and I found that the inner most wire was partially molten into a plastic housing of the unit and the insolation layer was flaky.

1. Is the failure of this transformer a known common fault?
2. Is the transformer itself the culprit or could there be a problem with a different electrical component?
3. What thickness of wire should I order to replace it in case I wanted to rewind it and solder back in place?

Any feedback is very welcome. I have basic knowledge in electro mechanics.

Dave
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Old 21st Jan 2021, 8:38 pm   #2
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Default Re: 1965 Mustang AM radio restoration.

Hi Dave, I'm unsure of the circuit of this radio, but it may be a vibrator transformer to provide the HT. The vibrators often stick and apply a constant 12v to the transformer causing it to burn out. The effect can also be caused if the radio was designed for positive earth and you connected it for negative earth.

Measure the bare sections of the wire with a micrometer and buy grade 2 solderable enamelled copper wire of the same diameter for your rewind

Ed
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Old 21st Jan 2021, 8:51 pm   #3
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Default Re: 1965 Mustang AM radio restoration.

A transistor is visible at the bottom right of the first picture, so unless the set also has valves I wouldn't think that's a vibrator transformer.

There is a second transformer visible which could be the output transformer.

Perhaps the OP could confirm whether the set has valves.
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Old 21st Jan 2021, 9:29 pm   #4
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Default Re: 1965 Mustang AM radio restoration.

I have restored a few old valve car radios and hybrid designs. I remember being surprised that these things bragged of being a transistor radio. The transistor is commonly used as a solid state vibrator. I think it may have been Motorola that did this first.
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Old 21st Jan 2021, 10:14 pm   #5
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Default Re: 1965 Mustang AM radio restoration.

Many car radios of the period were made using valves running at 12V HT. No way could they make enough power for a speaker, so one of the first uses of transistors in car radios was to have a TO3 cased device as the audio output stage, driving the speaker via a transformer. THe transformer primary also acting as the DC feed to the transistor collector.

Are you sure you applied the correct polarity? plenty of these sets were wired for positive earth.

David
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Old 21st Jan 2021, 10:19 pm   #6
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Default Re: 1965 Mustang AM radio restoration.

I have no idea if they are talking about the same (or even similar) radio

https://antiqueradios.com/forums/vie...p?f=1&t=104144

Quote:
My BIG problem is the audio output transformer gets super hot. Killed the power when it started to smoke. My question is, was the transformer initially bad or did I somehow cause it to heat up by changing the caps? Can someone recommend a web site if I have to replace the audio output transformer?
I know some radios had a single ended power transistor output.
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Old 22nd Jan 2021, 12:06 am   #7
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Default Re: 1965 Mustang AM radio restoration.

Thanks for feedback.

The case was negative ground and i wired it correctly, one thing to note is as i turned the switch the speaker jumped and held in tension - just like as if you put dc on its leads. No other response just smoke after few seconds from the Transformer. Its Motorola radio.
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Old 22nd Jan 2021, 10:41 am   #8
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Default Re: 1965 Mustang AM radio restoration.

Hi

Your radio looks like a Philco 5TPZ, presumably made on contract and badged Ford. Similar sets were also fitted to the Falcon and Fairlane models. I have no service data, but sets made in the early 1960's would have been just in the era of all germanium transistors, so no valves or vibrators.

Usually a single output transistor was used, running in Class A, and would have needed a reasonably large transformer between it and the loudspeaker. The output transistor dissipates a fair amount of heat, so uses the chassis as a heatsink. I suspect this is the TO-3 metal packaged device visible in your picture.

I think the choke/transformer is unlikely to have failed on its own. More likely is that excessive current has flowed through it due to a fault somewhere else or indavertent connection of a reversed polarity 12 volt supply.

The 1960's was a time when American manufacturers were in transition from positive earth back to negative earth, so I can't tell you what your radio would be designed for. Clearly, you need to find out before applying power again after repairs.

Last edited by Mr 1936; 22nd Jan 2021 at 10:44 am. Reason: Typo
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Old 22nd Jan 2021, 10:51 am   #9
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Default Re: 1965 Mustang AM radio restoration.

Hi (Again)

I have found that SAMS technical publishing (USA) list service data AR-28 which covers the similar 5TMZ radio. You can buy this as a download for $22.
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Old 22nd Jan 2021, 10:56 am   #10
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Default Re: 1965 Mustang AM radio restoration.

It looks to be similar to the 3TM(E,F,Y) series.

https://www.radiomuseum.org/r/motoro...a_18806.html#c

Cheers

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Old 22nd Jan 2021, 12:05 pm   #11
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Default Re: 1965 Mustang AM radio restoration.

Looking at the circuit suggested by Mike, a shorted output transistor would give the symptoms described. The output transformer is connected as an autotransformer (like a tapped choke) so heavy current through its winding will apply some direct dc to the loudspeaker by virtue of the winding resistance.

There's a fair amount of protection in the output bias circuit with two PTC resistors involved.

2N176 transistors do seem to be available though the provenance may be iffy.

You might get away with one of the usual local suspects like NKT404, OC28 etc.

Easiest "fix" could be just to build in a modern small cheap IC audio amp module.
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Old 22nd Jan 2021, 12:51 pm   #12
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Default

It is 5TMZ and its 12V neg. gnd. (Its stamped on the case)
I am sure i did not wire it opposite way, but i cant say what did a guy before me who sold it to me on ebay.

Is there a way how to test the transistor with basic houshold tools (12v, led-diodes, multimeter)?

I have a spare radio in much worse state, the actuall Philco unit for some spares (if usable because its 98% rusted due to fact the heater core was leaking and / or holes in cowl).

How does ic amp module work? Could it be fitted inside and keep the original use of buttons and am tuner? Which unit would you suggest and how would you wire it in?

I have aso ordered the folowing amplifier in case all fails - i could butcher the insides, use 5 limit swiches on the button assambly and hopefully the volume and bass knob (if they would wanna work - resistancy range) the only thing stopping me is that i wish to be it as original as can (within reason) be.

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Old 22nd Jan 2021, 1:26 pm   #13
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Default Re: 1965 Mustang AM radio restoration.

Thread on testing transistors with a DMM here:-

https://www.vintage-radio.net/forum/...ad.php?t=42194

You'll have to take it out of circuit to test it though.
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Old 22nd Jan 2021, 2:17 pm   #14
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Default Re: 1965 Mustang AM radio restoration. 5TMZ.

I think restoring vintage car radios is a nice hobby and they are still relatively low cost and small. I have always thought the most beautiful examples are the American car radios. I remember the one I found recently was a Motorola. https://youtu.be/fjgooJ2LKJE

I have a vintage looking radio in my Chevy but it’s actually a modern one with inbuilt MP3 but given the decline of broadcasting that’s probably for the best. But I would like to replace it if something vintage became available etc I did try to by one from American last year for little money but got blocked by USA customs as containing toxic substances LOL!

Good luck with your radio lots of people on the forum will help you get up and running again.

Chris
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Old 22nd Jan 2021, 4:12 pm   #15
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Default Re: 1965 Mustang AM radio restoration. 5TMZ.

Hi Chris, i agree with what you say!
About me really using AM radio today, not too sure - i remeber last time doing so as i was 8yo and was wondering what could i catch on grandpas old tube radio. But who knows i might discover something.

Id try getting the radio now since costums are bussy with more important things these days. Maybe it would come!

I wish to have the Motorola restored and running just for the feel of it being true original and and possibly even if it fully working add that second secret mp3 radio that would fit in an ashtray or glove box (just in case i wanted to listen to period correct music or even not).

I have to pick up my multimeter and test the transistor next week - ill inform you about the result in detail. Thanks all for posting your knowledge and advice. I am excited about how it will turn out!
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Old 22nd Jan 2021, 6:31 pm   #16
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Default 1965 Mustang AM radio restoration. 5TMZ.

Quote:
Originally Posted by Mr 1936 View Post
Hi

Your radio looks like a Philco 5TPZ, presumably made on contract and badged Ford. Similar sets were also fitted to the Falcon and Fairlane models. I have no service data, but sets made in the early 1960's would have been just in the era of all germanium transistors, so no valves or vibrators.

Usually a single output transistor was used, running in Class A, and would have needed a reasonably large transformer between it and the loudspeaker. The output transistor dissipates a fair amount of heat, so uses the chassis as a heatsink. I suspect this is the TO-3 metal packaged device visible in your picture.

I think the choke/transformer is unlikely to have failed on its own. More likely is that excessive current has flowed through it due to a fault somewhere else or indavertent connection of a reversed polarity 12 volt supply.

The 1960's was a time when American manufacturers were in transition from positive earth back to negative earth, so I can't tell you what your radio would be designed for. Clearly, you need to find out before applying power again after repairs.
Ford motor company owned Philco at the time, but the radio shown is a Motorola. Ford had an alternate manufacturer in case one firm couldn't keep up with the demand.
All the US manufacturers in 1956 went to negative earthng, when they went to a 12volt system.
Dave, USradcoll1
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Old 22nd Jan 2021, 7:27 pm   #17
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Default Re: 1965 Mustang AM radio restoration. 5TMZ.

Quote:
Originally Posted by daveoverride View Post

How does ic amp module work? Could it be fitted inside and keep the original use of buttons and am tuner? Which unit would you suggest and how would you wire it in?



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The IC amp module works by replacing all of the amplifier stages of the set after the volume control. Whether it can be fitted inside depends on how much empty space there is in the set and the geometry of that space relative to the module. If there's room inside (perhaps in the space vacated by the cooked output transformer) or even if the module has to be concealed elsewhere in the dash behind the radio then yes, the am tuner and pushbuttons etc can function as originally intended.

The sort of module I would envisage is one of the TDA2030 units available for a few pounds from Ebay sellers. This would also probably deliver rather more than the couple of watts of audio available from the original single transistor output stage.

HTH.....
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Old 23rd Jan 2021, 11:18 am   #18
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Default Re: 1965 Mustang AM radio restoration. 5TMZ.

I test that transistor later today but from what I see it's much more reasonable way then messing with transformer winding it or even trying to look for replacement transistor (if toasted).

Do you think, given better photos, it is possible to figure out where to solder the TDA2030 on? Would be a repair manual with schematics necessary? I found one and it's not too costly.
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Old 23rd Jan 2021, 11:56 am   #19
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Default Re: 1965 Mustang AM radio restoration. 5TMZ.

Datasheet for TDA2030.

https://www.st.com/resource/en/datasheet/cd00000128.pdf

A module would include the external components.
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Old 23rd Jan 2021, 12:13 pm   #20
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Default Re: 1965 Mustang AM radio restoration. 5TMZ.

If yourself (or anyone else) could post a copy of the 5TMZ circuit diagram (or confirm that the 3TM one in Radiomuseum is definitely the same) then the connection points for an amplifier module could be highlighted.

The module input needs to be connected to the volume control, the module power input to the switched 12V and the module output to the loudspeaker(s) in the car. This may be very simple or it might need some thought depending on how " negative earth" the set is signal wise given that it uses PNP transistors which are inherently positive earth devices. An accurate circuit for the radio would help work all this out into some DIY wiring guidance.
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