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AU-717,227080819,jd3rdcoast

Mostly it’s the original Rola 12” woofers in the HD/DS lines that are hardest to find. I have been very happy with my HD77’s and 88’s. Thay are designed for 250 & 300 Watt amps but still plenty sensitive for your 38. Might be able to find a set of HD 55, 66 550, 660 at a good price.

Ohm out the two points you want to solder the Cathodes to to check if they are a short, as in on the same trace.

I refurbished a 771 for a customer a couple of years ago. I was also blown away by the performance (for my ears). I dubbed it a Marantz 2245 Killer. I own mostly Marantz separates now but a 2245 was my first vintage purchase and I loved it. After the recap and new small signal transistors the...

Well, good news all. I updated the X10 and Tone Board transistors and that got rid of the oscillation noise as well as the popping on Tone Switch and Hi-Filter switches. :banana: I replaced all the NPN KSC1845's with matched BC550C's and the PNP KSA733's with BC557BTF's. The B has higher gain...

What’s weird is can’t really hear it and it sounds good going into my 250 without destroying it. Lol. But, I’m pretty sure it’s not right and I will get the proper subs. One more thing. The 1uf coupling caps on Tone were replaced with 3.3uf 63V WIMA’s. One of those were indicated as a...

Yea I was. Here is a couple pics of the signal measured at output of Tone board. You can see the noise in both (Right on top). The noise drops out showing the ringing I mentioned in second pic. Scope is set at 5mV/Div and .2uS time sweep. The extra noise is not present on Left side input from...

Thanks @ocdecio, I was starting to think the same. I believe it is oscillating. I will get a pic of the hi-freq noise. It looks like a ringing at the front end of a square wave on an amp but dirty, even though no input, then as the Vol starts up the dirty party clears up but the ringing on front...

Hi All, I am trying to finish up a Model 3300 Preamp that was restored by someone. Was brought to me not passing signal on right side. All transistors on the Phono/X10/Tone boards had been replaced with KSC1845 and KSA733's. I did locate a PNP transistor that was in backwards on the X10 Board...

170DC/3250B/2110 => Marantz HD88's. 2270 +> Marantz HD77's.

Q#1: Volume at minimum means just that. No Volume. Q#2: Some amplifiers by design do not have a DC Offset adjustment. They are balanced by the circuit design. Typically, if there is creep in DC then the differential amplifier pairs have drifted in gain matching and should be replaced with gain...

Are you sure on that voltage reading at speaker output? Seems that should trip it into protection mode and open the relays. You could try swapping the Left Pre-Out into the Right Amp-In and vis-versa with a patch cord. Then see if the hum moves to the Right side and Left plays fine. That would...

May want to post that board error in Marantz Service Manual Error thread. Search it first to see if already noted.

Check your work closely. Did you take pictures of cap orientation’s prior to work? Look for a broken wire, solder bridge, missed or poor solder joint. Check continuity from FM output pin to next point,

Zeners should not have been issue unless installed backwards, wrong value or test bad. Have you tried again with OT’s reinstalled?

From the ghost transistor department, I have had bad/noisy transistor on the phono card bleed DC noise onto the amp output. Disconnection Pre-Out did not resolve. Pulling the power wires to the Phono card helped isolate that. Rebuilt Phono = no more noise. In that one particular instance. YMMV

These are quite large compared to all other 1/2W diodes. From what little I could find the EQB diodes are 1W rated in several Sansui applications. So play it safe and order the 1N4742A 12V 1W 5% x2 and be done with it.

Typically, I will rebuild power supply, protection and amp driver boards as a good In-depth "tune-Up" since those circuits take the most abuse (heat) from high current.

If you think you will keep this unit ant want it to be in tip top shape then save the money up and invest in a restoration. Otherwise just use it as is if if sounds good to you. At some point it may exhibit audible issues and you can address them as they come up. Kind of like upkeep on a classic...

No, They are just across the RL03 coil.

Bone stock. Which is good, means no hack jobs by wanna be techs. That’s a plus. Probably just had controls serviced and amp bias and offset adjustment.

OK, that’s the way this circuit is designed with 2-12V in series. Don’t understand why they didn’t use a single 24V (which I have). But, they I’m sure they have their reasons. I also have 11’s and 13’s. Just no 12’s. Will order.

Replaced C17/C19. That cleaned up the feed toTR13-TR16. Still same noise levels on baselines. Then did some more scope probing and found some interesting waveforms. Need to get those 12V Zeners for ZD02/ZD04. I see a possible relation to our artifact. See traces below. Artifact on top and...

How about the 3000A after the cap coupling Service Bulletin application? I find it to be a great old school sound. The 800 is also one of my favorites. There's a 210 for sale locally for $80 and a 2000A for $120 (Powers on/No output).

Good eye Tarior. Yes, they are slightly bulged. While they are “newer”, they were installed by whoever tried to repair previously. Traces were burnt and lifted. I repaired with copper tape. But it’s possible they were abused. C17/C19 and they are on the +56.8 voltage that powers TR13-TR16 where...