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The original people from Northern NJ that had the FleaBay "wehavethatitem" were the same people you are talking about. But since he passed, his Wife sold it to other people. Her husband is the one that got the stuff in Florida. The "new" outfit however, began to sell counterfeits after that...

Cool. :thumbsup: I never had any DC Offset issues with the 730 that needed a trimmer. They were always under 5mv once warmed up. The Wards 450 was a little higher, but under 10mv so I didn't bother. I also always matched the input pairs along with shrink tube like you did though, which...

Did you add the trimmer for DC offset? That is the only difference I can see between this, and the Wards 450 receiver.

The A-402 amp board is slightly different than the 730 board. The Wards 450 receiver built by HK uses the A-402 amp board. Notice the 1S1211 diode position and silkscreen. There are other differences as well.

I never had to "bridge" any pads, unless there was damage.

The gain is more in line using the KSA1220AY and KSC2690AY Besides, only the lower gain KSC3503D is available. The KSA1381E is still available though. If you are getting stuff from @EastPoint get the 1220 and 2690 if he has them. If not I can mail you a few.

The KSA1220AY and KSC2690AY (the Uniwatt replacements) seem to have gone obsolete, although the KSA1220AY only seem to still be available. But I am sure @EastPoint has plenty of them. If not I bought a few hundred when I got the notice from Mouser. :biggrin:

No real sense trying to waste time for that, just rebuild it so you know it is all stable. Plus if the old BIAS pots go open, for even a second, the outputs could blow nearly instantaneously. An open BIAS trimmer will turn the output transistors on full blast at the speed of light. That's also...

If they are a latter production, the fixes could have been done at the factory. The service bulletin was to be applied at the authorized service centers if any unit came in for repair for any reason. Your serial number has the date encoded in it. You can submit your serial number in @LBPete...

Since it is old, it is easier for me to just rebuild the whole thing and have confidence in it. Most of the original carbon film resistors can be left alone as long as they are within 5%. They are usually closer to 2% or better anyways. If the traces give you trouble lifting, which can easily...

The original Uniwatt transistors often go bad too. They are the ones, usually pale green and gray, with the metal tab sticking out the middle of the body. They are center BASE, however the traces and markings on the silkscreen are there to use center Collector transistors as well. I used the...

Or the service bulletin was applied at some time. I replace the long pigtail fuses with short pigtail so they snuggle the board and don't pose a threat shorting out against the one Bridge Diode on the left, and the regulator transistor on the right. This is one board I rebuilt a few years ago...

Yes, ALL fusible resistors need replaced no matter how they test. The fusible element in the originals runs quite warm, and is why they are a metal oxide type, and stood up off the board. And as they warm up, the resistance many times also goes up throwing things off. If they are 1/4 watt...

Original trimmers? The carbon could have drifted high in resistance. Test them to see. Replace the BIAS trimmers minimum with Bourns. Using the old trimmers is gambling. Check for other resistors in the BIAS circuit. But, you never indicated if you set the BIAS cold, or when warmed up for at...

Any decent solvent based glue or adhesive will work. You don't need something fancy. They come under many brands. This one works fine and you can probably find something similar at a local hardware store, or even dollar store...

Yes... Before NTE bought ECG you can also search for ECG1339, and SPD1339 which are the same things. Click the link anyways... https://pdf.datasheetcatalog.com/datasheet/nte/NTE1339.pdf As always, check the datasheets of both the original and substitutes to be sure.

Nearly any 3.6v NiCad battery with leads will work. Something like this is smaller than the original 120mah, but will still work for a while. https://www.ebay.com/itm/395078459305?itmmeta=01HVMJWCE3SMHTHX9EVBC42GZY

The original 1S1211 is stood off the board positioned right next to the BIAS transistor where it will capture some heat. :thumbsup:

:rockon: :beerchug:

The one in the middle looks like it has been hacked up pretty bad. Skip that one for now. Rebuild the 1st one on the left. The main power supply board looks fine so replace the electrolytic capacitors. But the 3 small gray electrolytic caps along the pins for the driver board are Bi-Polar...

The originals are 100HMz, and the MJE15032/33 are 30MHz. Depending on the circuit design, it may or may not matter.

Blue cap to the left behind the first looks domed.

With the driver boards out, use a 100w Incandescent bulb. If it still gets bright, you have a problem somewhere and need to recheck your work.

The 1S1211 stabister diode could be bad. It is D408. A single 1N4148 should work pretty good there. Lower the BIAS before powering it off to change it. And always use an 8 Ohm load when setting the BIAS current. This unit does react to it when setting the BIAS and is mentioned in the SM.

Could also be related to those NTE substitutes. The MJE243G NPN and MJE253G PNP will work to replace the original 2SD669A TR507 (NPN) and 2SB649A (PNP) TR508 The NTE373 are too low current (1.5A) and are probably overheating. The MJE are 4A like the originals were. @EastPoint may have some.