Strokes are a bummer for sure. I was somewhat lucky, especially in view of the fact that I lived through it.
It did not affect my speech or cognitive skills, although some would argue that something has affected my cognitive skills! My balance was badly affected, I have to use extreme caution so as not to fall. My physical well being has been damaged because I get less exercise than I would if I could walk about more normally. I've had no problem driving. I had the stroke nearly five years ago now.
I appreciate Ed's cheerful willingness to help and I'm glad this turned into an interesting thread. Thanks Mitch for your post.

My own dad suffered several strokes, just shortly into retirement. He had so many plans for relaxing hobbies, like woodworking, travel, fly-fishing, possibly Hamming again, etc. All of that he had to abandon when he lost use of his left side. Arm first, then diabetes attacked his foot and he was in a wheelchair afterwards.

Undefeated by all the adversity, he proceeded to learn early computers together with me. He lived on the opposite end of the state from me. A visit or two a year was all I could manage, so we used the mails and telephone to communicate. There was no email or internet. Fidonet was just getting started back then, we both had 300 baud modems, but mostly we exchanged computer program cassette tapes by mail.

He wrote a western novel on his TI99/4a and still enjoyed life as much as he could. Just as he'd done all through his life. It was a diabetes-caused blood-clot stroke to his brain that took him in 1989. Pretty much all my skills and interests in photography, electronics, woodworking and cars derive from him. I still have and use a couple of his radios and many of his tools.

So yeah, that sure played a part in my decision to help Mal. Another unrelated thread had somebody asking why we don't have a step-by-step repair thread here in the Soiled State forum like they do for tube sets. Mal's radios sounded like an "easy fix" and I figured to have it all wrapped up in a tidy bundle in a week or so.

I keep forgetting 'ol Murphy is my next door neighbor, but he should remember I almost always win in the end. But still he tries to make life interesting.

So that's my story, and I'm stuck with it!

-Ed

Great to hear your Dad's and your story Ed. My son has been in a wheelchair all his life due to cerebral palsy. He and I are very close, but we're going to be less so physically soon as he is moving to an apartment building designed to be convenient for handicapped persons. He will also have access to public transportation - there's none here in Wolfeboro. Unfortunately his new digs are 98 miles away and so we won't see anywhere near as much of one another in this lifetime anyway. We have been under the same roof for 39 years!
Young Mal (we call him Malzy) is very bright and got himself a college education to boot. I understand his need to be independent and anyway, I won't be around forever.
Such is life.

We have some more pics to post, going back a couple posts to testing caps in-circuit. At first we tried our trusty DMM. It read a different value with the probes swapped between leads, as shown here. The part in question is a 100uf 10v electrolytic. We didn't learn the printed value till we'd pulled it, that's often the case on these crowded boards. So all we have to go by with in-circuit tests is what our various meters tell us. We mostly hope to find an area to concentrate on, as no way do we want to strip the typical radio down to test all parts individually. There's no schematic or any other servcie info. Usually we don't even bother to search for info, we just dive in head first!

There's another ongoing thread on the forums about the validity of such simple tests, and I admit the consensus is right. These tests are often inconclusive. But for many years when I was growing up and playing around with radios, a simple multimeter was all I had, so I made do with it. Later on, I upgraded bit by bit, learning as I went. With some practice, you learn to interpret the results using the gear you have on hand. I'm like you, I'm here to learn, so let's get going!

In the interest of perhaps demonstrating the results any beginner might see with various low-cost pieces of test equipment, we'll just try out what we have on hand here and see if it helps diagnose the problem. Then we'll move up the ladder and use a transistor checker, signal tracer, signal generator and other test gear to show what a better-equipped bench might help you to achieve.

We start with my Harbor Fright DMM. Probes placed one way across the capacitor, it read 1089 Ohms.



And with probes reversed, we see only half that, 510 Ohms.



The "resistance" of a cap is not really a very accurate term, but it's all we can measure using just a DMM. Typically, you'll see the cap's resistance drop to a low Ohms reading, as the cap is drawing current from the meter's battery to charge itself. As it collects a charge, its internal resistance rises and it takes less current. So we see this as a rising reading on a given Ohms scale. How fast it rises depends on the range chosen, the particular meter chosen, value of the cap, quality of the meter's battery, etc. So it's not a "constant" you can point to and say good or bad, but after testing a few good ones and bad ones of various values, there is indeed a correlation of how fast a meter reading changes. How long the meter hangs at a low resistance and how slow it rises are indicators of capacitance. This effect is more visible on an analog meter that uses a needle against a printed scale.

Eventually, resistance will climb above a given range on your meter. Switch to the next higher range and see if the cap is again in scale. Eventually, you will see the cap settle down to a maximum resistance reading. This could be called its leakage just to simplify for our purposes here.

Now that you've found a maximum resistance on your DMM or multimeter highest useable range, swap the probes on the cap and test again. You should see the reading go way down, maybe bottoming the meter needle or reading with a minus sign on your DMM. What's happening is the charge you just placed on the cap is being dissipated by your meter's internal resistance. While your meter is actually set to measure Ohms, you're testing a cap with voltage that was placed on it by the meter's bettery. Don't worry, it won't hurt your meter, as it's no higher than the meter's own internal resistance-checking voltage.

How long the reading sits in a reversed state depends on the actual capacity. Higher values take longer. If you get tired of waiting, try changing ranges. Eventually, usually only a few seconds, since it's only a few volts in the typical meter, you'll see the resistance again go positive and climb upscale once more. If all is well, it will again hit near that 10-20k ohm mark or better.

Keep doing this, swapping the probes and rechecking the resistance till you get a feel for what's happening. As a side note, you are actually "reforming" any old capacitors that have not seen voltage in awhile. Sometimes you will see the numbers improve after a few times. Note you did not "fix" the cap by doing this. But it does help explain why a set left on awhile sometimes improves a bit as caps reform.

It's also why you use a dimbulb tester on old tube radios, to help caps reform and take a charge. They may at first appear to be almost a dead short since they are so fully discharged when you first turn them on. It also helps explain why a daily driver may actually work better than one that has sat unused for a long time. Its capacitors are reformed by use and may be in better shape internally than caps in a totally neglected radio.

The marvelous thing a capacitor does is to help direct various frequencies and help us deal with AC and DC voltages which need to be separated from one another. That's why they are used in speaker crossovers as well as radios and about everything, really. They also store and release energy on alternate cycles of an AC wave, which is why some type are called "filter" caps. There's many types of caps, right now we are only dealing with small electrolytic types. And one noisy tuning cap, but dealing with that is coming up soon.

So, what we really need to check is how a capacitor behaves at the frequency range in which it is being used. Which, sadly, our lowly DMM cannot do. But, it can find some basic info and trends we can deduce things from.

In the case above, we learned that in-circuit resistance was masking any effect our cap in question may have had to say. The fact we got two different readings with probes swapped, that did not rise in resistance during the test, tells us we need to remove this cap to test it more accurately. The high/low resistance we see in-circuit when swapping probes at this particular location is actually due to a diode or transistor junction nearby, which in a way, is a positive result in itself, as we did not see a direct short nor an open at our test point. So, it's all good info, one way or another.

Once the cap was removed, it measured about 20k ohms. For an old electrolytic, that's actually not too bad. As noted in the thread, the radio did actually work, so it's not surprising to find this cap within "acceptable" limits for simple resistance.

I didn't try to choose a cap that would give me the results I hoped to show, I'm just picking one out at random and giving it a try and reporting what we learn by it. For a reference, we retested the same circuit location after removing the cap and saw almost the same readings. 20,000 Ohms wouldn't have much effect in parallel to 1,000 or 500 Ohms, so once again the DMM readings make sense.

Next, we apply our Tenma LCR meter to the same spot. It reads 14.19 uf. Since this is a 100 uf cap, it's getting pretty safe to assume this part needs to come out for leakage testing and replacement. We didn't know it was supposed to be 100uf at the time we made the reading since we couldn't view the printed value, but we figured on pulling all caps anyway as part of this repair. BTW, replacing all 4 electros in this set did not fix it, but in the process we eliminated them from the troubleshooting. All of them did test bad for rated capacitance, but none were appeciably "leaky" on the DMM.



While we're looking around, we spot a few solder connections we need to inspect for possible shorts. Apparently good, running a knife blade between we dislodge an old solder blob, but no improvement. Still, it's very important to check things closely. A single loose conductor strand from a breaking wire can render a set inoperable or intolerably noisy.



I also took a couple pics of the "crud" I suspect is at fault for our noisy tuning capacitor. I guess we don't know the source, but the parts set is beautifully clean in comparison. Just another thing to watch for to help explain noisyt operation and deal with at some point.





After this I pulled out the transistor checker, but we'll save that for the next post!

-Ed

Hi Mal, I was posting the latest session when you replied. Sorry to hear your son who has lived so close will be difficult to visit. As you say, he may need his own space at some point and it's never bad to achieve independence, even if the separation hurts a bit at times. There's many ways to remain connected these days that my dad and I had only seen the first glimpses of back in '89. I wish you both the best and hope you remain close.

-Ed

My "repair" posts are lagging several days after I actually did the work. I'm already a step or two past what I'm posting about, but I haven't gotten pics of it or written it up yet.

I'm following the replies with interest. I'll try the thermal checks, but don't expect it to show anything up. I'm thinking it's a leaky disc cap or off-spec resistor causing the apparent "warmup" time. But it's easy to try and illustrate, so I'll give it a coolant "shot" and see what happens! I had already tried heat from my soldering iron, as it happened to be right there in my hand, so the thought had occured to me, but cooling it might help find it, too.

Tracking bias voltage is a good technique I wish was easier to apply. I'm having trouble finding which circuit lands belong to a given transistor or other part, let alone determining which one is the base lead. There were only two transistors close enough to a board edge so that I could get the mini-clip leads attached to try my checker. Both tested good with no noise. I barely managed to test a third, it also was good. At least the checker identifies which transistor lead is base, emitter or collector and whether it's PNP or NPN. But finding the proper places to hold three probes while adjusting the meter was proving impossible so I gave up. Too tight to read part numbers or find the correct lands to probe. We may have to remove outer parts in the way to get at several of these for testing and/or removal, if t goes that far.

I did wonder about trying some probing of voltages during this warmup time. It's a little too brief to get much testing in before the set begins to work. But it sure deserves an attempt or two.

Some of what I'm illustrating may seem irrelevant to heading directly at the cause. I'm checking and replacing caps first as that's what the general consensus is on the forum to apply as a cure-all (or cure-most, anyway). Apparently not a cure-all in this case, but it was worth it to eliminate that factor and show how I go about testing them.

We'll try to eventually work our way around to trying most if not all of the various ideas presented. Please don't think I'm ignoring your input if I seem to be still working on an idea from several days prior, as that's when I actually did the work or shot the pics you're only now seeing!

-Ed

We understand your (remarkable) pace and we're with you.

I guess we're going on a week with no action, so it's time for a new reply! What can I say, with my wife out of town and two dogs, house, yard and chores to take care of, I've been bizzy!

I've pondered the problems between the two radios for a week and finally decided to concentrate on the "user" set and leave tracking down the odd noise in the "parts" set afterwards.

I figure that Mal has waited long enough to get his radio back. The scratchy tuning cap is a known problem, while the noise is sort of an unknown that may take some sleuthing, so we start this session with removing that pesky variable tuning capacitor.

It has two screws and three soldered connections. Here it is after removal, pretty typical for a solid state radio. We made note of which wire from the ferrite antenna went where and also noticed the two radios differed on how the antenna was connected into the circuit. I didn't try to understand why that was, but I made sure to get the wires back to where they came from in each set.



Next, we use a pocketknife to separate the cap's cover from its base. It's very flimsy plastic and I managed to crack it in a couple spots, so be gentle and work your way around the perimeter. It's only bonded in a few small spots, so it actually popped off fairly easily.



Tired of the dainty-handed Girl Scout approach I had been applying, I took the removed cap back to the workshop and blasted it with tuner cleaner from several angles, then followed that up with 80psi compressed air in a blitzkrieg effort to finally rid it of the crud trapped within.

Reinstalling the cap after this Power Wash, I was disappointed to find it was basically unchanged and still as full of pops and clicks as before. Bummer! Time to give up trying to fix this old cap and swap in the tuning cap from the parts set. Here, we're soldering the replacement cap back in. I managed to break one lead of the replacement cap while getting it removed from the parts set, but it had a long enough stub that I was still able to get a good solder connection.



The original cap has now been removed and reinstalled, then removed again. The terminals are very flimsy and by this time, it had lost part of two terminals. On closer inspection, I discovered I had forced some of the insulators from a smooth, flat state into a sorry-looking bunch of wafers. Offhand, I'd say I've managed to toast this tuning cap! Oh, well, that's how we learn not to apply really aggresive cleaning to such a delicate component.



Finally, upon installing the replacement cap, we're able to test again. This time, the popping noise caused by the grit in the old cap is now mostly absent. This cap isn't perfect, either, but at this point I'm not about to attempt a repeat of this little misadventure!

The result thus far is we're able to tune the "user" radio again, but find we're pretty much back where we started with it, lack of sensitivity on the low end of the band. I got out my diddlestick and peaked the coils and trimmers to KOA Denver at 850kHz while verifying it could still receive at the upper end of the band.

Next step in the process will be to finish changing out the electrolytic caps in this set and see if that cure-all shotgun cap-changing approach does me any good this time. It previously failed to make a difference in the parts set, but just for making the record complete if nothing else, I have to follow through on this set to see what gains there are to be had.

-Ed

Wow Ed, can you spare any of that patience? Regards the sensitivity issue, please bear in mind that WBZ (Boston 1030KC) disappeared one day. I then found that only our one local station at 1420KC could be received. Boston's about 90 miles as the crow flies, but a normally decent AM radio such as that Westinghouse once was, will pick up the major stations from that market.

It isn't so much patience as dogged determination, LOL. Plus, I'm hoping a few people might attempt a look inside their own balky transistor sets. Most of them will be cured and playing by now, but maybe it's good to see how various parts are removed and tested and the pitfalls that may await.

This thread has seen some views, but not that many comments of late. Somebody asked for a How-to thread, and this has become my version of one. Hopefully some others here will put their own methods on paper, so to speak and add their own threads to the forum.

It's mostly experience with other sets, but seeing good pics helps. I'm about half-stumped on these radios myself half the time, but maybe I'll teach myself something as we go along.

In a way, it's good to have two similar radios. When I reach a point with one, I grab the other and continue with it. And unlike a couple other sets I have waiting in the wings, both of these with boards flipped will fit on a sheet of paper.

Last night I finished changing all but one cap and thought that performance was improved. Today I put the last cap in and- dead set! Probing around where I'd just been, I suddenly got a second of audio. Tracked it down to an adjacent lead that I'd desoldered while removing the cap and never resoldered it.

That's a good reason for why I like to test after every part or two, there's fewer steps to retrace. OTOH, I don't know how many times I had to reattach a broken wire.

Speaking of, the first circuit trace came off while removing a cap. It joined just two leads, so I simply soldered them together. This board has been really sturdy for working on. The traces on some boards would be in tatters by now.



All the electrolytic caps have been changed now, and this time it seems to have helped. I'm finally tuning in some stations around 700-800 and still receiving the upper end of the band. Stills seems kinda quiet at the bottom, but at least I'm receiving something. I'll try it again for night reception.

So, to waste time while it was too baking hot to be outdoors, I moved back to the noisy set and refined my photoshop circuit trace.



From this, it wouldn't be too difficult to trace out where many of the parts are located on the circuit side of the board.

-Ed

I was hesitant to post anything, but of course you have tried generating a 540 Kc signal, with the probe next to the Ferrite antenna, rotated the tuner to that freq, and then adjusted the oscillator coil's slug for the loudest tone?

Hi fifties,
Not Yet. First was replacing the bad tuning cap that was too noisy to do anything, then I completed the recap. As a stopgap to an alignment, I tuned a 750 station and peaked the coil to it, then rechecked stations at other points on the band and felt I had a decent golden screwdriver alignment for now.

Thus far I've been working on it at the computer desk and didn't want to drag out the tracer and generator quite yet. I don't think it's an alignment issue at this point, but I did bring reception up a bit with a little diddling.

I switched over to the parts set for a spell while I debate putting on a sig gen or tracer or just heading in to test the transistors.

-Ed

Wow Ed, you've made real progress. As you already suspect, the alignment should not be an issue as it was good a month ago! As for alignment on the parts radio, I couldn't say. I'm dog tired tonight as today we swapped out a 45 year old refrigerator for a new one - just because. The swap over was my chore as I'm the only cook and bottle washer who lives here. So good night, I'll tune back in late tomorrow.

I'm back for whatever that may be worth.

We are still enjoying the thread and following closely for the latest results.
BTW, I picked up a no-name 6 transistor radio today for a buck which is from
the same era as Mal's. Don't know if I would/could/should make my own
version of a 'how to fix' thread also. But I will offer it up for a parts rig if Ed
gets stuck. Honestly, I only paid a dollar.

Eagerly awaiting the next installment,
~ Mitch ~

Glad to see there's still some interest in the thread! My wife's on her way back home on a long 1300 mile return trip alone by car, so I'm waiting for calls from her while she's enroute and meanwhile I'm making the house back into a home instead of a temporary radio repair shop.

I did stop housecleaning long enough to check the caps I pulled in the last session. My LCR meter showed no leakage on the 20meg scale, where normally it might, with a truly "leaky" cap, but the capacitance values read about 3x-4x too high on all three. 127 uf measured for a marked 30 uf cap seemed kinda odd. The replacements read much closer to the marked values. The radio did seem to be improved by the recap, but I don't think that alone has fixed it yet.

Mitch, sounds interesting, how can you lose for a buck? Why not take a few pics as you check it out and make a thread about it. The same basic techniques each of us have learned can be applied to lots of these old pocket radios.

-Ed

Funny that aged capacitors with no measurable leakage would have increased in value so drastically. Perhaps they didn't and were that far out of tolerance from the get-go.
Generally speaking, at least in tube equipment with much higher B+ voltages and AC ripple to combat, the more capacitance the merrier. I don't know how or if that rule applies when the power source is a 9-volt battery.

Hey Ed,

Inquiring minds want to know how the restoration is going.
If you're busy, I apologize. Not bugging ya... well.... ok... maybe just a little.

~ Mitch ~

Same here...

Sorry guys! I had to take a break from it to let my mind clear and a ton of different projects promptly moved in to distract me. I've had time for my usual learned reply to a forum topic here or there, but have done nothing useful radiowise!

I haven't forgotten it and I'm mentally pondering the next move. As a recap of where we're at, the player set still has poor sensitivity on the lower half of the dial. It's had a new resistor, a recap of electros and a swapped tuning cap. At least we haven't lost ground!

The parts set still has the hissy noise even with no tuning cap. I suspect we have a noisy part somewhere! I was taking meter readings while it was noisy before "warming up." Comparison readings between the two sets was inconclusive. Next is to let it warm up and try the cooling spray.

-Ed