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 Post subject: Arvin 65R58 10-transistor, dead... almost
PostPosted: Sep Tue 15, 2020 4:24 am 
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Location: moreno valley
All I can find are schems for the 9-transistor version but this radio seems to be the same as far as I can see except it uses a tenth transistor instead of the diode.
-- I recapped it, no noticeable change, still just popped when turned on though the vol control does make noise so at least it seems okay.
-- Then noticed the blade on the adj. resistor next to TR9 was not making contact so I tweaked it closed again and about where it was already set at. (All I can read on the schems for TR9 is "regulator" or "oscillator", not sure what that is?)
-- After that I could finally hear something, but only one or two stations, and even on headphones at max volume they are extremely weak and grainy with general background static. This close to dead, but not quite.

I'm sort of lost without any voltages specified on the schematics, and difficult to read these but I think I jotted my transistor measurements down right using the schems and board layout. I just bought & recapped a simple Micronta audio AF/RF tracer and it appears to work but I have never used a tracer before. Anybody see anything that sticks out like a sore thumb here? Thanks!


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 Post subject: Re: Arvin 65R58 10-transistor, dead... almost
PostPosted: Sep Tue 15, 2020 7:01 am 
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frenchmarky wrote:
I just bought & recapped a simple Micronta audio AF/RF tracer and it appears to work but I have never used a tracer before.

Time to learn. I would suggest that you get a simple 6 transistor radio and use the tracer on it, starting at the speaker and working your way back to the converter, testing at each Transistors base and collector elements.

Once you have a feel, then do the same with this circuit. When you get to the point where the signal increases, you have found the culprit stage. Then do some voltage measurements on that stage.

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 Post subject: Re: Arvin 65R58 10-transistor, dead... almost
PostPosted: Sep Tue 15, 2020 7:04 am 
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Arvin 65R58 was covered in Sams TSM-60
I don't have it!

Greg.


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 Post subject: Re: Arvin 65R58 10-transistor, dead... almost
PostPosted: Sep Thu 17, 2020 10:36 am 
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Thanks, I've got a few 6 and 7 transistor Arvins that I've fixed up, will try the tracer on one and see what I get since the designs and parts probably have similarities. Tracer seems to work and amplify well on the AF sections of this radio so far, but of course it's basically just really loud background noise right now. Will see if I can dig up the board trace layout for the working one(s) so I don't have to yank the chassis out all over again etc. and can just test it with the back cover off since they are all trace side facing out.


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 Post subject: Re: Arvin 65R58 10-transistor, dead... almost
PostPosted: Sep Thu 17, 2020 4:23 pm 
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TR-9 is the bias regulator for the audio output. Have seen the adjustment pot go bad (oxidized wiper contact). You could try a bit of De-Oxit or try an external pot to find needed resistance and then replace with a combination of fixed resistors to replace as I had to do on one.

Also measure the voltages from battery pack to ensure all contacts good. Have seen one contact be resistive and cause low voltage on one leg of split supply.

Good luck !

John


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 Post subject: Re: Arvin 65R58 10-transistor, dead... almost
PostPosted: Sep Thu 17, 2020 7:36 pm 
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The contacts on one end of the batt pack did have that green crud on them but I filed them clean and it's getting solid 9V coming in and 4.5 for the lamp. The adj. pot's blade was lifted and not making contact at all but I corrected that and put DeOx on it and it does seem to be operating. When turned end to end at max volume, it ranges from nearly zero volume to pretty good if I have it on one of those stations I can hear, but still very weak and grainy and the background noise drowns it out.

Hey does it matter whether the radio I'm testing is oriented with the transistor voltages as negative, or as positive? I.e. do I need to switch the tracer leads around if I am testing the RF/AF depending on the polarity of the transistor voltages?


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 Post subject: Re: Arvin 65R58 10-transistor, dead... almost
PostPosted: Sep Fri 18, 2020 5:05 pm 
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Well for the first time in about 30 radios I finally goofed bad enough that I blew something else while testing and made it worse, while checking out the audio section using another radio and linking the outer lugs of the volume controls. Now I'm back to just a pop when turned on. I'm putting this one aside for awhile because I'm too ticked off and don't want to look at it anymore. At least I did get some experience with the tracer trying it on a different radio, both the RF and AF parts seem to work okay on the tracer.


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 Post subject: Re: Arvin 65R58 10-transistor, dead... almost
PostPosted: Sep Fri 18, 2020 8:58 pm 
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The two voltages circled in RED indicate the RF Amplifier transistor is saturated (about 0.1 V between the collector and emitter) and will not be amplifying. This could be due to a failed (shorted) transistor, an open resistor (circled), or an open coil (circled). There may be something else going on, but that is where I would start looking. Other voltages all look reasonable.
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 Post subject: Re: Arvin 65R58 10-transistor, dead... almost
PostPosted: Sep Fri 18, 2020 10:40 pm 
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Image

I pulled up Sam's TSM 60 page 30.
If any want a CLEAR copy send me your Email by PM (will send by PDF file :wink: )
I limited this to 640 but the original is clearer.


THE PREVIOUS SCHEMATIC DOESN'T LOOK QUITE LIKE This posted SCHEMATIC.
heres the voltage readings.
All transistors are PNP

RF Amp X1 B= -.6V C= -7.5V E= -.4V

CONV X2 B= -1.1V C= -7.5V E= -1V

1st IF X3 B= -.7V C= -7.2V E= -.5V

2ndIF X4 B= -.6V C= -8.1V E= -.4V

DET X5 B= 0V C= 0V E= 0V

AF AMP X6 B= -.4V C= -6.2V E= -.3V

DRIVER X7 B= -.6V C= -8.6V E= -.5V

OUTPUT X8 B= -4.7V C= -9V E= -4.5V

OUTPUT X9 B= -.2V C= -4.5V E= 0V

BIAS X10 B= -1V C= -3V E= -.4V

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 Post subject: Re: Arvin 65R58 10-transistor, dead... almost
PostPosted: Sep Fri 18, 2020 11:43 pm 
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Start tracing at the driver and work towards the RF stage by stage. If you can hear it weakly then your audio is at least functioning.
Use this link to help you to troubleshoot. Its a Sam's book that's free! Transistor Radio Servicing (PDF)

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwiN5cfmjOLrAhXyCTQIHah-Cy0QFjAAegQIHxAB&url=https%3A%2F%2Fworldradiohistory.com%2FBOOKSHELF-ARH%2FSams-Books%2FTransistor%2520Radio%2520Servicing%2520Made%2520Easy%2520-%2520Wayne%2520Lemons.pdf&usg=AOvVaw0MmDiQ51r4J0GcdHV0-BV8

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 Post subject: Re: Arvin 65R58 10-transistor, dead... almost
PostPosted: Sep Sat 19, 2020 6:34 am 
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Thanks everyone, I'll get back to this one next week, need a little breather from it. The audio section did seem okay from the loudness of poking at traces with my soldering iron and the crackles from my probes but I was trying to verify that for sure and apparently 'blew' something else in the process. Or it finished off what was already half-blown. I'll first check all the voltages again against the above.


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 Post subject: Re: Arvin 65R58 10-transistor, dead... almost
PostPosted: Sep Sat 19, 2020 7:50 am 
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It's hard to imagine that you "blew" something out, given a nine volt power supply with minimal current. Could be though that you shorted a Transistor on it's last legs. I doubt any passive component was or could be harmed.

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 Post subject: Re: Arvin 65R58 10-transistor, dead... almost
PostPosted: Sep Sat 19, 2020 2:45 pm 
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For future reference all voltages should be measured relative to the common ground which in this radio it the positive terminal of the battery. I saw from your measurements the battery must have been measuring 9.1 volts and you used the negative terminal as the reference, so I converted your measurements to those that "would have been measured" if you had put your meter negative lead on the positive lead of the battery. Having done this it is now possible to directly compare your measurements with those provided in the other schematic...
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The upper voltages in BLACK are those in the schematic, and the lower are your converted measurements. BLUE voltages are all reasonable.

So clearly a big problem exists right at X1 right at the Collector. Again this could be due to a Collector to Emitter short on X1, an open coil or an open resistor. Collector to Emitter shorts are not uncommon with old PNP Germanium transistors.

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 Post subject: Re: Arvin 65R58 10-transistor, dead... almost
PostPosted: Sep Sat 19, 2020 4:06 pm 
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Curtis put together an excellent chart !

Open coil windings on transistor sets are rare but DO happen. And resistor itself may be okay, but you might have a poor solder connection or cracked circuit trace in that are---have experienced both in other transistor sets of that vintage.

Also have seen Arvin sets of that type with cracked PCB's at corners near mounting points causing intermittency---probably from dropping or rough handling. Some of these can be hard to see unless you hold a bright light behind the board.

Let us know what you find !

John


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 Post subject: Re: Arvin 65R58 10-transistor, dead... almost
PostPosted: Sep Sat 19, 2020 7:01 pm 
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PDF Schematic sent to frenchmarky.
Thanks to all who contributed information.

Hope there is enough to get it fixed.

Even I learned a thing or two. :D

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 Post subject: Re: Arvin 65R58 10-transistor, dead... almost
PostPosted: Sep Sat 19, 2020 9:57 pm 
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+1 on Curtis's effort!
In my experience, Transistors seldom seem to die, but of the ones that do, for whatever reason, the converter is usually the culprit.

Definitely verify the passive components in it's circuit, and if all is well with them, ya need another Transistor to replace it with.

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 Post subject: Re: Arvin 65R58 10-transistor, dead... almost
PostPosted: Sep Sat 19, 2020 10:23 pm 
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With all this new info I decided to dive in again. I feel guilty like a doctor who cut off the wrong leg. :)

-- Tested a couple of transistors but the voltages were now halved from before, ugh. So...
-- measured voltage directly at the battery terminals, it too goes from 9+ with radio off to only 4 or 5 with radio on.
-- The lamp doesn't light up anymore now either, but bulb does light when tested and can hear 'click' in speaker when I activate the lamp switch. (I do still get buzzing from the speaker when probing certain transistors with the soldering iron, just not as loud as before so the radio doesn't seem completely dead.)
-- Whether radio is on or off, lamp switch 'on' drags the battery all the way down to less than half a volt.

So it appears to me there is now a short which is measuring about 50% of battery voltage when radio is 'on', but whether radio is switched on or off, when the lamp circuit is completed the short is nearly total. What could be shorting that isn't even getting to the guts of the radio when completing the lamp circuit, but still partial short with radio on? Maybe the 200uf cap connected to the lamp circuit got shorted during my audio testing? Would or could this be the culprit, or something else? (I replaced it with two 100s during the recap.) Thanks!


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 Post subject: Re: Arvin 65R58 10-transistor, dead... almost
PostPosted: Sep Sat 19, 2020 10:48 pm 
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A battery needs to be tested under load conditions.

Try the battery in another 9 volt circuit while measuring it when the unit is turned on, if you don't have a battery tester (or even if you do). If it still shows 1/2, toss it and test another. You need to verify 9 volts in the subject's power supply when it's on, to get accurate readings.

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 Post subject: Re: Arvin 65R58 10-transistor, dead... almost
PostPosted: Sep Sat 19, 2020 11:09 pm 
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About current Draw.
stick a multimeter in series with the battery.
The current should be around 16ma, @ 9VDC (No Signal, Min. Vol.)
The current should be around 25ma, @ 9VDC (Signal, Normal Vol.)

X8 terminal guide
( EB C )
. . - .
----------------------------------
X1 through X7
............................ B
.......................... . .
........................( E . . C) . <-- Terminal
-----------------------------------
X10
............................... B
............................... .
......................... E . . C
TAB ->
-------------------------------------
For opens and Shorts
Check C10 (.02)
Check C3 (10mfd)

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 Post subject: Re: Arvin 65R58 10-transistor, dead... almost
PostPosted: Sep Sun 20, 2020 12:19 am 
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Ah-hah, the battery pack does drop way down connected to one of my 9V Zeniths as well, barely runs it. I didn't think the batteries were it since before, the lamp lit great but immediately after the audio test not even a slight glow, zilch, so perhaps whatever I did while I was doing the audio testing, and for how long, and perhaps a partial short, finished them off.
-- Put new batteries in the Arvin, lamp now lights, battery voltage now only drops .03V when on, but no change in radio, just a pop when turned on.
-- Amp reading with my meter(s) set to 20ma or 200ma shows off scale with radio turned on.
-- Activating lamp with radio off measures .15 amp at 10amp setting but then that matches with this GE109 lamp.

So not sure exactly what amps the radio is drawing but looks like over 200ma? Putting two different meters on 10amp setting just shows zero or 0.02 (20 ma) which don't match with the off scale readings when set to 200ma so dunno if the 10amp setting on the meters is just not reliable for this particular amperage or what. I'll see if I can dig up a 9v wall socket adapter in my box cuz it sure looks like this thing may be eating my batteries up. But the pack has a center tap at the other end for 4.5v so I can't just use an adapter instead, right?

I suppose it's possible that if this is indeed a shorting problem it existed from the start, but I don't think so since with the new batteries it did not improve the radio's performance back to when I was getting weak reception with the previous batteries.


Last edited by frenchmarky on Sep Sun 20, 2020 1:20 am, edited 1 time in total.

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