Harmon-Kardon TA 230 Stereo Festival

[electra225]

I have one of these that I've had for almost 40 years. I don't remember where I got it. I used it in the garage for eons. I was never impressed with its performance. I listened to AM radio mostly. FM performance was mono without a Multiplex adapter, and was only so-so. I had cheap speakers on it, so that is one reason. I haven't had it plugged in for a long time. This is one of those things I just never got rid of. The 6408's were gone when I got it, so it has a mismatched set of 6V6's in it. I've never done anything to it. This might make a nice project one of these days. I'd think it should sound much like an 88 or 93 series Magnavox amp or my Dynaco SCA-35 if all is right with it. I believe it has 22 tubes or thereabouts.

[electra225]

I dug this old thing out this afternoon while I was waiting for record player parts. I brought it up slowly on the Variac and dimbulb. I got it to full voltage, drawing 127 watts. Rating for wattage is 175 watts. I found one channel dead, or nearly so. Wiggling the 12AX7's brought it to life. It has really dirty controls, particularly the "phasing" switch and the balance control. Dirty tube sockets, too. I noted earlier that FM performance was only so-so, but I can close the eye tube on FM with just a test lead for an antenna. AM performance was okay, considering the directional action of the loopstick antenna. An external antenna pretty much too care of that. I didn't try the phono stage at all. I had my bench speakers connected to it, and they are only 5-watt jobs, so I had to be careful to not give them too much volume. There are four bumblebee caps, coupling caps in the audio output section, .047uf@600 volts that should be replaced. I'll check resistors and that while I'm there. I need to find service information for this. There are controls on the output tubes that probably should be adjusted for maximum performance.

[Hi-Fi-Mogul]

Wow, I looked up what this baby was, and it looks impressive !

RadioMuseum says it was set up for dual AM/FM stereo broadcast, which
I always thought was an amazing concept someone came up with.

https://www.radiomuseum.org/r/harman_ta ... stiva.html

I found this neato link for you, Greg, for when you start on the Stereo Festival.

https://hudsonvalleyhifi.com/wp-content ... _TA230.pdf

[electra225]

Thank you so much, Mr. Mogul. That diagram will sure help.

R5 and R6, the output balance controls are cathode bias adjustments. They want 25 volts on the cathodes, I assume at "idle" or with no signal. I don't see anything to indicate that for sure. I remember not being terribly impressed with the performance of this receiver back in the day. I'd think it should sound as good as a Dynaco SCA-35, or a Magnavox with P-P 6V6 output.

[electra225]

I recapped it, set the cathode bias, cleaned every tube socket, every control. I did improve FM performance with a light alignment tune-up. I found a weak 6AQ8 FM RF amp, a genuine Amperex tube. Changing it did help FM performance, sensitivity mostly. This receiver has a tuned AM RF section, so it has a pretty hot front end, on both bands. The audio performance is just not impressive. It is bright and crisp, with no distortion, but it has extremely anemic bass in my opinion. I tested all the tubes. I believe it's as good as it will get. I think this one will be for sale. It is impressive in appearance with it's shiny tube shields and is nicely laid out and well-built. I'm a little disappointed that nothing I did to it really helped how it sounds.

[TC Chris]

Looks very impressive! The AF caps are all OK?

Chris Campbell

[electra225]

I replaced the only paper caps in the chassis, all four of them. I checked resistors. I checked the cathode bypass components. The rest of the caps are ceramics. The filter caps and B+ all check out. The bass response is wimpy. I seem to attract instruments like that....

[Motorola minion]

I always liked H-K equipment and this is one example. Long ago at a huge yard sale, I found an A-300 amp and T500 tuner with built in mpx for like 20 bucks . This receiver looks like a combination of those separate components, especially the amplifier.

I will agree that bass is pretty disappointing, as P-P 7408 (6V6) rating of this amp was 12 watts RMS per channel.

It has a very sweet sound if used on efficient speakers with a magnetic phonograph cartridge, like a Dual 1009 with Pickering V15. On line inputs, it is not as nice but clean.

[electra225]

Dave, you mentioned you had dim 6DA6 eye tubes in your project. This one has nice, bright eye tubes, IIRC, they are 6FG6's. One for each radio band, which is kinda neat. I'm going to connect the Fisher speakers I have to the Marantz 2245 to get a baseline on the speakers. Then I'll connect the Stereo Festival to them and compare. That may be like comparing a Piper Cub to a P-51, but it will give me a better idea of just what I have. I have the CD changers or a couple competent turntables I can use to see if phono performance is better than radio performance. It is a beautifully-built piece.

[electra225]

I am dinking in the shop, trying to talk myself out of the SX-1050 project. I put this receiver on the bench and connected it to my little RCA 45 player. I am using a set of Fisher speakers with 15" woofers. The 45 player, of course, is not stereo. I connected it's ceramic cartridge to the "Extra" inputs, since both phono inputs are for magnetic cartridge. I connected the output of the 45 player to the left input then turned the mode switch to "monophonic". This let the sound come out of both speakers. A nice feature of this receiver is that when you are in a non-radio mode, the eye tubes are dark. IF you switch to AM or FM, the opposite eye tube is dark. There is a dial, an eye tube and a tuning knob for each band. The audio with the 45 player is nice and clean, with gobs of volume. As noted before, bass response is disappointing. The little Radio Shack amp I use on the bench with 1.8 WPC of solid-state output makes more bass than the Stereo Festival with P-P 6V6's. If I turn the balance control so as to cut off one speaker, the remaining speaker has more bass. It seems like with the balance control in the middle it attenuates the bass. That sure doesn't sound right. The AM eye tube does nothing. The FM eye tube does deflect, but not much. My next task is to connect this receiver to a "good" stereo turntable with magnetic cartridge, as recommended above, to see what it does. Every tube in this receiver, with the exception of the four output tubes, is in a shield. If this thing had a bit better bass response, it would be an impressive rig.....

The big Fisher speakers surely help bass response. I haven't connected the SX-1050 to them yet, but I think I'm going to like those speakers.

[TC Chris]

Your speakers aren't out of phase, are they?

Chris Campbell

[electra225]

Good question. All I can say for certain is that they are connected to the receiver and that they make sound. They are located in corners of the shop, buried. One has "whatever" stored on top of it, the other has a brass fan setting on it. I need to run the wiring to make sure positives and negatives are right. My guess at this point is that they are not. I really had no intention of using these speakers. I have console stereos I was going to use and not mess with component stereo equipment. The best laid plans of mice and men......

I can share, however, one positive thing. Dave was right in his comment above. This receiver badly suffers from the same identical malady as Magnavox bi-amps. Wimpy bass response in the tuner and auxilliary inputs. I connected my $3 Accurion DJ turntable, equipped with my favorite cartridge, a Stanton 500 magnetic to this receiver. I will have to admit that bass response is quite adequate, considering 15 WPC audio output. Bass response is at least as good as in my Symphony. The speakers I am using are Fisher STV-884's, that the audiophools generally poo-poo as not desirable. Fine. I played my Magnavox Concert Grand demo record, an Eddy Arnold record and a Jerry Lee Lewis record and I'm pleasantly surprised. I don't reckon I have ever used this receiver on a turntable before. Just the radio and tape inputs. There is a 12AU7 tube, in a shield, that gets screeching hot, hot as an output tube. I don't think that is right. I touched the shield and burned my finger. The rest of the "little amplifiers" only get warm. Why this tube gets so hot should be investigated. I need to see what the speakers are rated, whether they will take much of the SX-1050 with the volume control advanced or not. I'm guessing not. I may go thru this thing component by component and set everything up right. Maybe even a set of matched output tubes. I was only tinkering. I had no idea this thing is a real receiver when used with a magnetic cartridge.

[electra225]

The speakers are rated at 110 watts, so they won't take the SX-1050. They are not highly regarded, considered junk by the "experts" so they should work out fine for what I'm doing. The gripe about them is boomy bass and chintzy cabinets. They were apparently built during the period where Fisher quality was declining. Research reminds me that I gave $35 for them at an auction in 2012. I got them by outbidding a flipper. I was advised that I should have let the flipper have them......

[electra225]

I just learned another amazing fact. I get better stereo separation, and better bass, if I put the mode switch in Stereo, rather than leaving it in monophonic like when I was playing 45's. Don't ask how I got so smart so fast......

This is going to be my next project. It's on the bench and has parts that are familiar to me. I'm going to need a coach like Chris had if I attempt the SX-1050. I'll go thru this thing thoroughly, then use it for my shop stereo.

[electra225]

The schematic calls for 375 VDC on the plates of the 6V6's, and that at 117 VAC line voltage. With 120 VAC on the line, we will be approaching 400 VDC on those plates. The tube manual gives 350 VDC as max plate voltage. No wonder the output tubes aren't original. The 12AU7 that is running so warm is a Sylvania tube. No idea when, and by whom, it replaced the original tube.

[TC Chris]

The speakers are rated at 110 watts, so they won't take the SX-1050.

Remember that amplifiers are rarely operating at anywhere near their maximum output power. They are almost always in the range of a few watts unless you are trying to make the neighbors move away and make yourself eligible for hearing aids. Under-powered speakers amps cause more damage than over-powered ones by going into clipping and burning up the tweeter voice coils.

Chris Campbell

[electra225]

The SX-1050 is really hard on tweeters. I don't remember having burnt out woofers with it, but it used to eat tweeters. I never did figure out why. I don't know if you remember them or not, but Radio Shack used to sell stand-alone tweeters they called Super Tweeters. Outside of Peavey horns, these were the only tweeters that would stand up to the SX-1050 for any length of time. Peavey studio speakers would take everything the SX would give them, even if I used an equalizer. I had a set with 18" woofers that I couldn't kill, couldn't get them breathing hard......

[electra225]

I started running the resistance chart on this receiver this afternoon. So far, all I found was some 470K ohm resistors that had drifted, one of which was in the plate circuit of the 6FG6 eye tube for the AM band. I've just gotten started, so I may find other resistors that are out of tolerance. I need to break down and buy a new, accurate digital meter to measure resistance. The one I have is cantankerous.

[TC Chris]

My ohmmeters are all cranky as well. I was contemplating buying a good DMM the other day. Fluke is the one name I recognize. What are other good bets?

Chris Campbell

[electra225]

I won't spend the money on a Fluke. I had one of those when I was wrenching. I wasn't impressed. I had the Snap-on guy send it in three times to have it repaired. They never did get it right. It's only redeeming value was that the case was cushioned, so it wouldn't hurt it if I dropped it onto a concrete floor. I was thinking of maybe seeing what Harbor Freight has. Or Home Depot. Something in the $20 range. I'm hard on small meters. I forget to change ranges and usually end up frying the ohms part of it. I don't use digital meters for anything except measuring resistance. My Fluke meter went to the landfill one day following a particularly cantankerous outing on a TV chassis.....