HH Scott 342-C: Why do Scotts seem to get overlooked?

This guy had blown output transistors on one channel so I mounted NJW21193 and NJW21194 transistors cutting short and soldering wires to the collector and emitter leads so I could cross them since On apparently quit making the MJE2801 and 2901 in the TO-247 package some time ago that would match the old ECB pinouts. Seems like everything is BCE now and with the the new guys rated at 250W versus the old 90W ones hopefully will be hard to blow them again.

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Took me some time to find it but a previous owner had installed a toggle switch and led to the 47k resistors in the signal path soldered to that side of the selector switch being half blown away. Replacing them along with a broken solder trace on the preamp board got the tuner back clean and in stereo. Before sometimes the left channel worked with varying levels of distortion if it worked at all. The right was missing the lower frequencies. Replaced with a push button and moved it toward the outside some more to get enough room for the stuff soldered to that side of the selector. Need to find a better looking washer but it will do for now. Also had a sizable channel balance problem and if you look carefully at the picture above the diode in the middle pushed up against the transistor socket on the left card I finally spotted and straightening it back up and that fixed the balance problem. Noticed that when I hooked it up to the KLHs. Recapped it originally hoping it would fix things that helped in some areas but not all. After replacing the resistors it still had a big hum problem. I decided to cut the two ground strips at the tone board and removed the part on the pins so the board could seat better. I ran a new ground wire on one side and took the existing ground wire on the other side that ran to the preamp board and input selector and tied them to the ground point next to the big pot in the middle of the chassis which apparently adjusts the tuning meter. Also did another round of deoxit on the volume control. I left the ground wires running between the tone board and amp cards alone. Hum now very low but still audible with the volume at minimum. Redid the FM STEREO and PERFECTUNE lights with red and green leds (latter was burned out) found I had to put about 100 ohms in parallel to the to the leds and limiting resistors to get the circuits behaving properly. With just LEDs and limiting resistors they stayed lit. Started high kept dropping resistance using alligator clips to hook them in found 100 ohms got the circuits working as they should. The PERFECTUNE light will faintly flicker at times between stations. Amp bias and dc offset adjusted to spec with the new transistors the dc offset on the left channel dropped a lot along with the hum after fixing the grounding issue.

When I finally got it back together tonight finally succeeding in getting all the bugs out I was surprised how good this guy sounded with my test KLH model 403s. They are small and nothing to brag about but if something makes them sound good it is likely a winner. After passing initial test period with those moved it and hooked it up to my vintage KLH Model 17s. This guy after all the repairs is a very good sounding little receiver. Might not win style awards but nice tuner. Have not tested the phono section yet.

Sounded even better with the KLH 17s once I figured out that like Sherwood with my S-7200 they have the loudness on by default. You have to push the button in to turn it off. I am not a loudness fan. This guy may sound even better than my S-7200 but not as good as my Sansui 2000A with the Hoffman mods but it seems very competitive with those two.
 
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And I see Scott at this time was into modular construction which made recapping a lot easier than some others I have done in the past. I gather this was produced before the original company went bankrupt back in the early 70s. Capacitors and semiconductors different look than contemporary stuff built in Japan. Looks like all semiconductors Motorola with a few Callins and Whale capacitors most only have Scott part numbers and the two filter caps had Syncro on them. Also the little axial polarized caps were different too. Boards and chassis before the recap and repair.

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A lot of HH Scott early transistor gear gets overlooked due to styling and fewer of it out there. However, for one with an open mind, who loves awesome performance, solid USA build quality, and impeccable engineering, the wise HiFi buff should pay attention to HH Scott. Up to 1973, with the demise of the original company, and a bit beyond their gear is superb.
 
The styling is pretty basic compared to much of what else was out there. Looks more like it was built about a decade earlier. It did not go for much in an auction. Was thinking I might have a bad preamp chip thus making it a dud but managed to work it all out. May be like the reputation of the Sansui 3000A - not very appealing to look at but once you hear one in good working order the looks may grow on you.

Was trying to figure out what in the world PERFECTUNE was when working on it and it became obvious it is like a center tuning meter and helps you more accurately tune in on the signal. The stereo light comes on first then you more precisely tune to try to get the PERFECTUNE light to come on. On weak and noisy stations it probably won't come on.

I think I confused the numbers on the NJW21193 and 21194 transistors. They have a 200 watt Pd on them not 250. Still much higher than the originals. After playing for an hour or two the output transistors were reading about 100 F with my IR thermometer.

If anyone in the future is looking for replacement bulbs for the dial and tuning meter they were small bayonet 1845 bulbs. Like replacing backup and brake/turn light builbs in an older car. I ordered these from Digikey:

https://www.digikey.com/product-detail/en/visual-communications-company-vcc/1847/CM1847-ND/3151342
 
I've had more success finding good clean plug and play early Scotts for $100 than anything else from that era. From 1966 to 1972 they sold like hot cakes. I think they are over looked because of the knobs and small compact cabinet size. And they made to many different models. With different knobs and a wood cabinet the size of the Sansui 1000 it would be quite impressive. It seems they didn't understand the changing market. The 477 would have been the cure but it was the wrong color. To little to late. My 342-C owners manual was printed in 1969. I'm thrilled with mine. Overall it gives up nothing to any other receiver I have. Total lack of sound color. Plenty of power at 30 watts.
 

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The 477 is the black one. At 70 wpc it should be impressive if this little 30 wpc guy is any indication.

That is one virtue they have. It is much smaller in size than virtually anything else I have but it is not light. Easier to make room for it.

Caught another error. The MJE2901 and 2801 are the originals. I meant to say I found in the datasheets On used to make the MJE3055 and 2955 in a TO-247 package with the ECB pinout that would have been a drop in replacement but they apparently quit making those some time ago. The current T models are BCE.

Played a CD through the EXT1 last night after my posts nice neutral sound seems to be doing good job controlling the woofers in the KLHs keeping a tight clean bottom end. Very likeable. I was up late I tend to be a night owl by nature but when I finally get a problem child working good it is hard not to listen to it for a couple hours and put it through some paces. Especially when it had been looking like it may be a dud with a failed hard to find component. So far so good.

I think there is an adrenaline rush that goes with fixing something, especially if it was complicated and has taken a good bit of effort. I get some pieces in rough shape with problems and get them back working again. It is like solving a complicated puzzle you have to figure out as you go along. Greatly increasing my understanding of solid state electronics. More mechanical in nature (BSME and MSME from VT in the early 90s) but can do some electronics and electrical. Those couple EE classes we had to take the basic part was not too bad, but I think the second one where they dealt with transistors had most of us MEs confused.
 
The 477 is the one receiver I want the most. If it had come out all silver they might have been in the thick of the race. And I can probably get a nice ready to go one most anytime, for $500. They're going for $200 plus silent. So I wait.
I rarely make any repairs other than lights so I'm thrilled when a receiver jumps out of the box throwing strikes. I'll sit up all night with a new toy like the 342-C.
 
Thank God the Scott stuff is overlooked; it hasn't been hyped like Marantz/Pioneer/Sansui and thus can be had for reasonable dollars. I've had a Scott R74S receiver for ten years now and it hasn't needed anything except some pot cleaning. I'm listening to a Scott 420A integrated amp right now and it sounds very good. No, it doesn't go to 11, it's not 165 wpc RMS, and it's rather modest looking, but it's so simply and cleanly built that I imagine it would be rather simple to work on if anything went wrong (nothing has). There's a lot of empty space in the chassis and an absolutely huge raw aluminum heat sink in there so unless one blocked the top vents I can't see it overheating. My 380R receiver has everything: IEC cord, triple tone controls, power meters, subsonic filter, connections for two TTs and two tapedecks, massive xformer, etc. and continues to function well while several other universally coveted receivers failed outright and needed major surgery to produce music again. The mystique surrounding the big names was created by decent sound but also by extensive advertising in major publications such as Playboy. The Scott stuff is just as good, just not as well known.
 
Styling. Scott tubes looked great except for the brown faced units. The first ss units had the LK-72B / 299D look but that did not last.
 
The achilles heel of the early Scott solid state units was the output stage. First of all it was quasi-complementary, which meant it had a single supply and 1/2 the supply voltage on the output, so it has to have a capacitor in series with the output. Never good for sound. The second problem was the adjustment pots go open and nuke the output stage. Boom. Always replace the trimpots. The tuners are ok, but they only have 3 gang tuning caps. They can be sensitive enough but never good selectivity. Most of the Sansui receivers have at least 4 gangs. I have a 342 someone gave me that I am going to upgrade the power supply to a positive and negative rail supply and put a better amp in it.
 
A HH Scott solid state specialty was their tuners, both FM and AM. So fine, many broadcast stations used them for on air monitors, program relay over the air, and engineering functions. Their SS tuners were among the most sensitive on the market, with excellent selectivity. The 312D broadcast monitors are superb, my example gives you 1.6 uv sensitivity for full quieting in Stereo, among the best available in 1967. And superb audio quality.
 
The second problem was the adjustment pots go open and nuke the output stage. Boom. Always replace the trimpots.

I'm working on a later model (R75s) so driver circuits are clearly different. So perhaps this doesn't apply at all--if so, ignore my noise. But I don't see how the pots going open would nuke the outputs. It would just eliminate any biasing, which would be distorting, but not immediately destructive. I looked into changing them but its very hard to find stocked 275ohm trimpots.
 
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unaffiliated for sure, but guy in my antique store wants to sell me a couple - a 342C and a 299F

PM me if interested and I will pass on contact info...
 
I'm working on a later model (R75s) so driver circuits are clearly different. So perhaps this doesn't apply at all--if so, ignore my noise. But I don't see how the pots going open would nuke the outputs. It would just eliminate any biasing, which would be distorting, but not immediately destructive. I looked into changing them but its very hard to find stocked 275ohm trimpots.
The circuit is set up so that if the bias pot opens up. it supplies full current to the outputs.
 
Doing a google search for the Scott 342-C and newspapers.com as the search terms comes up with a number of newspaper ads selling the 342-C mostly in the 1969-1971 time period. About the same vintage as my Sansui 2000A and a little ahead of the Sherwood S-7200. Not the most sensitive or selective FM tuner but makes FM pleasant to listen to. Actually these three 30-40 wpc receivers make FM more enjoyable to listen to than some of my more powerful ones.

I think the trimmer on the MPX board on mine that controls the muting/stereo level was going in and out, or it seems to be the best explanation for the fm being normal volume, then like it was muted, then coming back on normal volume. It got where it was going back and forth a lot and it was getting annoying. Tried the Deoxit/Faderlube treatment on the trimmer pot and FM was like it was muted when I powered it back up, I wiggled it a little and the FM came back in strong and clear. So far it has behaved for the last hour or so. I think I will be replacing the trimmer pots on the amp card and that trimmer next time I do an order from Mouser or Digikey, probably when I tackle the Pioneer SX-9000 I have on the shelf. I usually do but this one was badly distorting the FM on the tape monitor output when I did the initial testing so I wanted to see if I could get it fixed and operating normally before putting in new trimmers on the amp card. I was afraid this one had a bad tuner section. I did the deoxit/faderlube treatment on the amp card trimmers while overhauling. Looks like they use the same type trimmers as the 342-B based on the pictures of the B model I could find online.

Every once in a while I hear a little odd noise in the background of the left channel. It pops up and quickly disappears. Long periods between the noise right now. Past experience with that kind of noise its usually one of the amp card transistors ahead of the outputs showing early signs of going south. Ended up being a 2SA666 pair on the S-7200 and a pair of 2SA844 on my Yamaha CA-610II. This noise is more similar to what the 2SA844 transistors in the Yamaha started doing. The two that started acting up in the Yamaha were in the channel that had a blown driver transistor when I got it. I think the side starting to act up in the 342-C is likely the one that had the blown output transistors.

I like the challenge of fixing the guys with problems. I figure I am saving one from oblivion where it would get buried in a landfill or ripped apart in e-recycling. One more that will hopefully get to be enjoyed by others in the future. Fixing the electronic and physical issues can be like solving a complicated puzzle. Sometimes takes several attempts to get right. Requires a lot of patience at times. Better have patience when restringing a tuner. Many I can get for $80 or less. The SX-9000 was $25 outside of Charlotte sat on CL for months unclaimed and the project unit after it is the infamous Sansui 3000A that was acquired for $34. The former mouse infested (plus stink bugs) Pioneer is pictured in this post:
http://audiokarma.org/forums/index.php?threads/receiver-id-please.805193/#post-11213305
 
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I think I found the MPX board problem. It did well last night but tonight fm muted when powered up and trimmer manipulation did not get it. Pressing on the board on the pins at different angles would get fm to intermittently return to full volume. Looking at the board multiple times I finally noticed a cracked ring solder joint failure at one of the little grommets they use to connect the traces on the back of the board to the traces that run on the top side of the board. The other boards are fairly flat but over time the MPX board has developed a noticeable bow. Apparently the width with the weight of the components has been a bit much for it. Will see if melting that joint and some others will now have the fm section behaving normally. So far so good it came on at full volume.
 
Good find. Those are called feed-thrus or vias and the rivet kind are primitive and develop intermittent connections as you saw. The Sansui 9090dB has a Dolby board with about 40 of those suckers on it that become intermittent and have to be rebuilt by running a wire through, bending it over on both sides and soldering it on both sides. You should do this to every feed thru on this board to make it reliable. Soldering only is not good enough.
 
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