After replacing about two dozen electrolytics, my Sony 8-301W portable works great, except that I can't bring in the horizontal frequency (using frequency adjuster R4 and the horiz. hold control).

Capacitor C34 is 1mfd/12v. I couldn't find a 1-mfd electrolytic, so I used the closest I could find, a 3.3mfd/16v. Just wondering if the value of that cap is that critical?

Here's the horizontal portion of the schematic:

http://antiqueradio.org/art/temp/Sony8-301WHorizontalSchematic.jpg

I highlighted in yellow five caps that I replaced in this section, including C34.

Here's the full schematic:

http://antiqueradio.org/art/temp/Sony8-301WSchematic.jpg

If it's important to use that value, perhaps someone could tell me where to find a 1mfd/12v electrolytic. Mouser didn't seem to have any.

If 3.3 mfd is close enough for C34, then I'll start looking for other causes.

Thanks!

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

Did you look for a cap with a rating of 25V or 50V? Iuf is a common value; but, probably not at 12V. A more common 25V cap will work fine. It's quite possible that the 3.3uf cap could be throwing the circuit off enough to cause your problem.

Sure enough, they have 1mfd/25v. May as well order one and give it a whirl.

Regards,

Phil Nelson

That's a funny circuit (compared to the typical horizontal oscillator-driver-output in most sets I've worked on), so I'm not sure why it seems to want feedback from the collector of the output. But definitely the 300% increase in the cap, would flatten the feedback pulse, and that would cause a stability problem if the circuit is looking to that feedback for some reason for syncing or stability. It's my guess, that it's something to do with the AGC keying, but still....

Go with the 1uF @ any voltage 12v or > .

Charles

Without knowing the value of L13, it's hard to guess if the 1 uF is supposed to be tuning to a certain frequency or is just decoupling. In case it is tuned, I vote for keeping the 1 uF value correct.

By the way, not sure how much to trust this schematic, since it shows two different waveforms both on point #60. (The waveform on point #61 seems to have a false copy pointing to #60.)

Yes, I noticed several differences from the schematic, including one electrolytic not shown at all in the photo of the board it's on. Where values didn't match, I stuck with what was in the TV, figuring it must have worked when it left the factory. Everything looked original -- no signs of previous service.

The parts list describes L13 as "Peaking (500uh)."

I'll have a new cap in a day or two, so we'll learn then whether 1 mfd makes a difference.

Thanks!

Phil Nelson

Unless I'm pushing the wrong buttons on my calculator, that coil and capacitor resonate at about 7 kHz, about 1/2 the horiz frequency, so changing to 3.3 uF definitely could change things.

My fingers are crossed. Here's the best I could get (the TV is lying on its side):

http://antiqueradio.org/art/temp/Sony8-301WHorizontalOff.jpg

A familiar scenario. Fewer and fewer slanty bars as you turn the adjuster. You feel like you're only one more turn away from a good picture, and then the adjuster can't turn any farther.

The TV may still have a multitude of other problems, of course, but it can't hurt to replace that cap with one of the right value.

Phil Nelson

Silly me I thought this thread was about the 80's color set you fixed, and when I read the schematic I thought "Wow they were still using HV rect tubes in the 80's....who'd of thunk it".

You're 85-90% there, don't give up !

Fixing the 1980s set inspired me to haul this one off the shelf. When I got it last year, I didn't have an ESR meter. Now I have no excuse for ignoring it. With that meter, you can check every electrolytic in the TV in no time.

The construction is interesting. Tightly packed, of course. The boards are surprisingly heavy and everything is hand-soldered (not very neatly). I'm not comfortable with solid-state things in general, but this is more my speed than the 1980s Sony, with all of those black-box ICs and components the size of a grain of rice.

Phil Nelson

Hi
I restored 3 of these a few years ago,I remember one had problems with the horizontal oscillator running off frequency and took a bit of adjustment with cap values to get it back.

From the picture the oscillator is running only just a little bit high though,from memory mine was very low.

I was told that with electrolytic caps at that time the stated value would be the minimum and could in practice be higher,never lower.

I managed to make some pcb connector extenders which would plug into the main chassis clear of the set and plug any of the boards into them enabling work on an individual board while the TV is running to be carried out which helped a lot.

Hugh

Check those diodes, maybe one is a tad leaky.
Check or just change C98/99
C100/101 could defiantly cause it.

Thanks for the tips. I will look at those smaller components if the new 1-mfd cap doesn't cure it.

Sure would be handy to have extender cables to work on this. Very few of the interesting test points are accessible when it's all put together.

Regards,

Phil Nelson

Didn't get far today, but I found that installing a 1-mfd cap for C34 didn't magically cure everything.

Say that one of those AFC diodes (X28, X29) is bad -- what type would I order to replace it? The parts list only gives a Sony part number (1T261), which didn't turn up anything in a quick search. These diodes are teeny-weeny, not the type of thing I have in the parts drawers.

I'm starting to suspect there's more going on than simply being off frequency. Watching it for a longer time today, the vertical isn't as stable as I thought, suggesting maybe a problem in the sync section or something else that affects both vertical & horizontal sweep.

Maybe I was too generous when I checked all the electrolytics and passed about half of them as good. A failure rate of 50% (at best) is pretty awful. If I had the right parts on hand, I'd be tempted to shotgun the rest of 'em. That's a crude approach, but you can't reach anything with a scope probe when the TV's assembled, and I can't see building custom board extender cables that I'll never use again.

Phil Nelson

You want to get the oscillator speed down as quickly/easily as possible to see what else is going on,if I remember right I think it's possible to adjust L14 and that moves the frequency,have a look and see if you can (may be wax in the thing securing the core) and try 2 turns of the core in and note the effect and then go the other way if not right.
I just found my Sams manual on the TV,C99,C100 and C101 were certainly changed.Never had a problem with the sync diodes but type shouldn't be too critical.
It can be frustrating working on this TV......

On weak signals or with contrast low the sync can be be weak which is maybe what you're seeing.I block changed most of the electrolytics caps in the set,certainly if any linearity/height problems go straight for the ones below the height/linearity presets.

Youtube video of it here http://www.youtube.com/watch?v=StbCuBM3lA0

Good Luck

Hugh

Thanks, I found a new electronics store today and came home with a little sack of caps to try.

I have been using a weak signal, broadcasting from the modulator on the far side of the house. It will be easy enough to hook up a signal generator or DVD player and see whether signal strength matters. A static test pattern may make it easier to see what's happening, too.

I will try to find time to change C98/C99/C100/C101 sometime later today.

Phil Nelson

Say that one of those AFC diodes (X28, X29) is bad -- what type would I order to replace it? The parts list only gives a Sony part number (1T261), which didn't turn up anything in a quick search. These diodes are teeny-weeny, not the type of thing I have in the parts drawers.



It's likely a geranium diode, like the kind used in older transistor radios as a detector. A silicon diode like the 1N914 might work, though I'd change the pair to keep them the same type.

___brief thread interrupt-germanium diodes are useful with some evp experiments.the diode method for some reason works best with germanium types.

___back to your program

It's likely a geranium diode, like the kind used in older transistor radios as a detector. A silicon diode like the 1N914 might work, though I'd change the pair to keep them the same type.

I second the guess that they are germanium. Are they clear glass with copper color inside?

Do you have a scope to check the waveforms? This circuit wants the approx 5 volt pp waveforms shown on the schematic.
As stated above, L14 should affect the frequency. The oscillator is controlled by the voltage that is generated by the two detector diodes and filtered by R108, R109, C36, C99. R4 sets the center voltage on the detector when the frequency is correct.

If there is no setup procedure, I suggest setting R4 and R10 to mid range, and then see if you can get the right frequency by tuning L14. However, optimum might be with L14 tuned slightly to one side of center and R4 adjusted to compensate.

Wahoo!

http://antiqueradio.org/art/Sony8-301WHorizontalFixed.jpg

I think replacing C100/C101 turned the tide, although I replaced some other not-very-related caps in the same session.

You can tell from the snowy picture that the signal in my shop is weak. Even newer TVs look snowy, and there's lots of interference from CFL bulbs, wall warts, & whatnot.

I do have a scope, and it would be interesting to use it on this TV, but that's impractical given its construction. When put together so you can power it up, it's basically a brick. The boards are stacked so that only their edges are accessible.

http://antiqueradio.org/art/Sony8-301WChassis3.jpg

Anyhow, it looks like I'm on the right track. Both horizontal and vertical seem very stable. I'll play it for a while using different sources, to see how it holds up, before I decide whether it needs more new caps. I may replace a few more regardless, since I bought more today and rarely work on these new-fangled low-voltage gizmos.

Thanks for the advice & encouragement.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

Congrats! great picture

I couldn't resist quickly hooking up a pattern generator. Had to turn the gain way down, as its signal is strong.

http://antiqueradio.org/art/Sony8-301WTestPattern.jpg

The screen geometry isn't too bad. Not sure what's going on with that warp on the far right edge. This set has almost no horizontal adjusters, so I may just live with it.

In addition to vertical height and linearity, it has an adjuster (R5) called vertical bias. Anyone know its purpose? I don't see any mention in the manual, and I don't recall anything like that in old tube TVs.

Incidentally, I was wrong about it being impossible to access the boards while powered up. The alignment instructions in Sams say that you can pull either the rear or center board, unscrew its socket(s), slide the socket(s) out through the mounting hole(s), and then plug the board back in. Presumably there is enough cable slack on the sockets to enable this. I may try it tomorrow, just to see if it works.

For the record, the manual also gives a procedure for setting the horizontal frequency, first adjusting the stabilizer slug B1 and then the horizontal frequency control as I was doing in the first photo. Amazing what you can learn when you slow down long enough to read the manual. (When I was a technical writer, we had an acronym RTFM, which I won't decode here.) Possibly, I could have tried this in the first place and avoided replacing so many parts, but that wouldn't have been half as much fun :)

Phil Nelson

Good to see the TV is working !.

I can see some stretch on the left hand side,compression in the middle and a bit of stretch on the right side,horizontal linearity isn't so good on these TV's.There's the adjuster preset on the other side of the chassis tied in with the horizontal output transistor to slightly vary,may help,look in the manual and see if it recommends what to do with it.Not seen the warp effect on the right side before.

Your vertical linearity looks good,adjusting that preset you mention gives a non lin effect in the middle of the vertical scan I think,think best to leave alone looking at your picture now!

Make sure the 2SC41 horizontal op transistor isn't running too hot,the heatsink should be gently warm to touch and not roasting after say 20 minutes.Some early versions of that transistor tended to get very hot,for one of my 8 301's I took one out of a scrap later 9" set and it ran much cooler.

I think some of those connectors on the chassis underneath have short ground wires,may be wrong.

Hugh

Yah, the horizontal linearity is currently stretched somewhat on both margins, not on one side alone as I often see in older sets. The manual doesn't say a lot about horizontal adjustments, just telling you to use the stabilizer slug and frequency control to achieve lock, and then:

"Adjust Horizontal Drive control for best linearity. Repeat adjustments if necessary."

When I was fooling around with adjusters before reading that part, I found the Drive control and tried using it in the customary way, adjusting until you see a light drive line and then backing off a little. A drive line never appeared, but I noticed that the Drive control changed horizontal centering, so I centered the picture for the time being and left it at that.

I will check the temperature on the 2SC41 transistor as you suggest. I can also check its voltages shown on the schematic if that section is accessible when the center board is removed. I'm curious about that whole board-pulling scheme. If you really can power up the TV with one board or the other pulled out, that would be good to know for future reference.

Phil Nelson

The drive control alters the width a little bit I found.

Some sets have extra small value HV caps fitted across the horizontal scan coil wires where they plug into the board,they alter the width...

I think you can see why they dumped the model quickly and went onto the
the little 5" set.

While you're measuring volts I had problems with low volts for the video amplifier supply which is rectified from the horizontal op stage,changing the diode for a modern type fixed it.

The diode is near the transformer at the top of the board,you can just about get to it to measure with the board in place I think,or check on the video amp which is on the middle board near the top.

Hugh

Me no unnerstand a lot of the technical stuff y'all are talkin' here, but it seems that this set came by the nickname "Sony's Fragile Baby" honest...(grin)

Congrats - The noisy pic looks stable, so I think there's no more to do regarding sync.

The stretching of both sides of the H sweep is usually a design issue, depending on choice of components in the horizontal sweep section. Some sets have a deliberate "S-correction" built in that shapes the horizontal yoke current to reduce the scan a bit near the edges, but this one may not. There is no adjustment for it even if it's built in.

I went ahead and replaced the rest of the small electrolytics. It makes a decent picture now. This is from a test pattern DVD:

http://antiqueradio.org/art/Sony8-301WFaceTestPattern.jpg

http://antiqueradio.org/art/Sony8-301WFaceTestPatternCU.jpg

This TV is extremely sensitive to signal strength, making me wonder if there's something funky with the AGC. The gain control is very reactive, and I may need to adjust the gain when switching from one DVD to another, not to mention switching from one source to another.

The warp on the right margin is worst with a white-background scene like this. It was not apparent at all, and the width was more than adequate, when I played a DVD of Gone With the Wind on the same player.

The vertical hold is not as stable as I expected. Not awful, but not great, either.

It also has a noticeable hum, even with volume turned all the way down. This is not your typical intercarrier buzz, although I cautiously adjusted the ratio detector secondary (A9) as directed in the manual.

The TV is watchable in this state. Perhaps some of these nits are just in the nature of the beast. I don't want to flog it trying to squeeze BMW performance from a Chevette, but I want to improve the vertical hold, at least, before quitting.

Phil Nelson

Hi

There isn't any AGC on this TV I think,that's why it has this gain control and is critical in adjustment.The Philco Safari is the same,though has a 3 position sensitivity control,it seemd only the "second genration" transistor sets had something as exotic as AGC.

"Contrast" is preset on the middle board with that little control,so sort of set that for best looking picture when happy with the gain setting...yes this set is a weirdo!!!

The gain control is a dual ganged pot,one part attenuating the antenna signal and the
other the IF gain.I found it was better connecting the antenna in at full gain all the time
into the tuner,or one could end up with a slightly grainy pic but the IF gain about right,just resolder the coax inner going to the tuner to the top end of the pot where the signal is coming in via the same thin coax.

Try running the TV from a 12 volt supply if you can and see if the hum goes
and what happens to the picture bending effect on the right side.If you haven't the right DC sony connector brown wires in the TV are the 12 volt line I'm fairly sure.

Around the sync separator stage there's a 100K resistor which wasn't fitted on the pcb
on one of mine,holes there but never been soldered in...fitting that cured sync problems that set had.

You're getting there...

Hugh

I could be nuts, but the Sams manual calls X5 the "AGC amp" and it seems to take input from the 4th video IF as well as from the manual gain control. I am not good at puzzling out solid-state stuff. In any case, it behaves a lot like my RCA 630TS, whose manual gain was called the Picture control. A better label might have been the Twitchy control :) .

Having full gain from the antenna at all times seems good for my setup, where the old TVs primarily receive signals from the in-house modulator.

The hum definitely sounds like 60hz. Trying a 12vdc supply should be easy enough. I haven't examined anything in the power supply yet, since it plays plenty bright and plenty loud. A p-s can have noise interference even if it supplies adequate voltage, though.

Phil Nelson

Hi
I never really paid much attention to that part of the circuit as no problem with it..It's a very poor AGC system for sure...Make sure C19,30uF in the AGC circuit is ok or you might end up with some video modulation on the AGC line.

Playing with mine just now on a strong signal the video can be "moved" a lot within the screen by adjusting the normal line hold control at the rear.If it's
almost losing lock one one max setting that black curvy part as in your picture appears on the right side.Increasing the manual gain control (on a strongish signal anyway) forces the line oscillator to have a wider pull in/lock in range.

Hugh

It's interesting how the controls interact and how different signals affect it. Here's the same DVD machine playing different program material:

http://antiqueradio.org/art/Sony8-301WScarlettCU.jpg

For this DVD, the gain was turned up higher than for the test pattern DVD. No gap on the right, and there's probably still some warping, but not much you would notice.

Now that it basically works, I can spend some time finding the best compromise with the various adjustments. I'm still curious about that vertical bias control, too.

I was hoping to avoid it, but I need to remove the CRT to recoat the bell with Aerodag graphite and clean the inside of the safety glass. The CRT is shedding flakes of aquadag and some of them end up inside the cover. If you look back at the earlier photo of Hilary Swank, you'll see a big black flake that's not present in later photos. I tried blowing them out with a little rubber hose, and just created a mini blizzard of black flakes, so the old coating is not done shedding.

Phil Nelson

Well, it IS over 50 yrs old...(grin)

Kinda makes the RCA 8PT series seem simple to work on, by comparison.

jr

An interesting comparison. The 8-PT and 8-301W are both compact portables with stacked chassis (er, boards) surrounding the CRT neck. The clever lads at RCA even made it possible to slide the PT subchassis back on their rails, leaving things connected, so you can power up the TV in its "exploded" state.

http://antiqueradio.org/art/rca1606.jpg

http://antiqueradio.org/art/rca1605.jpg

After I finish off this guy, maybe I will sit down with both schematics to compare & contrast. The 8-PT sets are pretty nice performers, all things considered.

Phil Nelson

Is this yoke ringing?

http://antiqueradio.org/art/Sony8-301WRinging1.jpg

http://antiqueradio.org/art/Sony8-301WRinging2.jpg

Obvious when brightness is turned way up (first photo). The bands are stronger on the left and fade toward the right. Not so obvious when brightness is more normal (second photo), but you can see slight waves in the horizontal line that match the vertical bands seen in the first photo.

One of my TV books says that yoke ringing (if that's what this is) can be cured by replacing an open yoke balancing capacitor, but this TV appears to have no such capacitor.

If there's no simple cure, then so be it. I'm more curious than concerned, not having seen this in other TVs.

Phil Nelson

Ah yes,they all "ring" to a greater or lesser extent.

Check the rectified supply from the horizontal output transformer feeding the video output transistor hasn't any ripple on it C39 10uF would be the chief suspect.
.
Removing the tube isn't so bad,getting it back in is harder I think,had to do the aquadag on one of the CRT's also.

This was really one of the first transistor TV's,Sony had no history of making them before
and learnt from the experience on their next models.The thought with servicing seemed to be as a TV shop if you had a fault on a panel send just the bad one back to them for replacement.

There was a portable transistor TV made by Perdio in the UK in 1962 that looks very similar in a way with the front push buttons,it used the same CRT as the Sony though had a plastic case.

http://www.thevalvepage.com/tv/perdio/portorama/portorama.htm

Access to this was much easier,all the panels just swung outwards on a frame much like the RCA one.The TV was a bit "strange" in performance,though it did have good AGC.
~
Hugh

GREAT read Phil!!

This and the thread over on antiqueradio will give me enough confidence to dive into the 8-301W I just couldn't leave behind at the swap meet Sunday. I did go ahead and download the SAMS for this unit on their site. Was only 15 bucks....so likely the easiest way to learn the most about this little set.

You may recall from the other forum that I joined BOTH these forums because THIS set is likely to change me from merely a collector to actual restoration. The cosmetics and the fact that the set is 100% complete made me buy it in the first place. The worst that could happen from giving the guy $30 he wanted, would be to end up with ALOT of really great sheetmetal and knobs to pretty up another one, so it was a no-brainer really.

This was actually the VERY first time I had seen one in person. I walked by the thing like four times in the span of a couple hours. I had ONLY seen a couple on ebay...ALL with issues or REALLY rough looking described outright. I wasn't gonna SLEEP well Sunday night if I didn't at least have a go at this :-P

Mine DOES come up, but does have some classic electrolytic symptoms such as "takes like 10 minutes to stay synced", and has linearity issues for just about that same ten minutes. At first I kept "cleaning it up" with the controls and tweaks....only to turn it on a couple hours later and see it "back in trouble again". I learned Monday to just LEAVE it run and having issues, and then around 10 minutes later it eventually looks "just okay". There is some weird horizontal issues that stay though. real bad tearing if you see something like white text on a black background...and still a persistant little static sound in the audio that will come and go. Sounds JUST like a bad volume pot, but touching the pot (after cleaning them all up) doesn't change it. It'll make this static thing for like 15 seconds or so...and then be FINE for like ten minutes, and then do it again.

I'd REALLY like to have this set all pretty. It's BY FAR the neatest looking little set I've run across...and is even older (1961?) than the Sony 5-303 my Dad gave me (around 1965?).

It's only cosmetic issue is it looks like someone at some point had whacked the sun shield against something. I had VERY carefully wrapped just the sunshield in a dishtowel and slowly pounded it flat again with a rubber mallet. It still shows a little crease though where it was bent, but I can work on that later..... not anywhere near as dramatic, and it now "fits" correctly on the little rails on either side as well. This crease (and pounding it back carefully) didn't even crack the VERY hard to duplicate original "crackly stuff" that case and shield are painted with.