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Jack, Anwesh, and Brice, Thank you for your suggestions and advice! It's really made me take a step back and broaden my options. The TO-310s were purchased without very much foresight because I love acrosound transformers and these became available. I had wrongly assumed that I could simply...

Along these lines, I have a pair of Acrosound TO-310 OPTs and want to build a stereo PP amp. Since the Hafler Acrosound circuit has issues with distortion at higher outputs, I wondered if Dave's circuit (post #117in the Magnavox thread referenced above) would be appropriate for use with a...

Here's a picture of mine that I rebuilt a couple of years ago. I found the ribbon cable kit that I purchased on ebay to be an essential part of the rebuild. The old cables disintegrated as I removed them. Hope this helps!

Mine does NOT. That goes for other top/high end Pioneer tape decks, including the CT-F1000, CT-F1250, RT-707, and RT-909. The most common issue with lettering is that the red labels are more fragile than those printed in black. Hope this helps!

I purchased a set of the cables within the last year or so and was entirely satisfied with the quality of the cables as well as the documentation. It turned a potentially problematic restoration into a relatively easy one. Thank you so much for making these available!

Resurrecting an old thread for which no comments beyond the OP were provided. I arrived at the same conclusion as the original poster. Experimentation showed that a 50 ohm resistor could replace the 2.2k and be sufficient to limit current and still allow the circuit to work. Also, seems...

Dec 21, 2014

Steve, I had the same problem when setting up my 500C for Tung Sol tubes. I found that all attempts to vary the resistor values in the IBBM failed for the exact reason that you stated: adjustment range was reduced. By changing the value of the dropping resistor on my EFB, I was able to...

Has the OP checked pin 15 of the Power Supply PCB for 5.6vAC?

Incorrect in my case. The fuseable link connects the one of the two 5.6vAC heater windings to the main power board. If it is blown, the relay drive transistor Q301, does not turn on. clinic-audio, I know you are very experienced and knowledgable, much more than I am. I'm only saying that in...

Here it is, seen from the bottom side, near the front panel. The wire is covered with teflon tubing, bridging two of the terminal positions with a fuseable link. I used wire wrap wire, which measured between #30 and #31. Checking the current capability, they are very close so I went with it.

It's not a PCB trace on my board. It's a very small wire connecting two terminals where the brown 5.6 heater windings connect to a 3-position terminal strip. The MC2125 manual states that you should replace the wire with a 1-inch piece of #31 wire.

Are the front panel lights working? I've been working on restoring an MC2125, which is very similar. Suggest that you check for 5.6vAC on the power supply board (pin 15). If it's not there, the relay will not pull in because Q301, which controls relay drive, needs 5.6vAC. In my situation...

Big Ben, check your PM.

I just have ordinary access there. Perhaps your registration has not been completed?

You might give this thread a read: http://www.tapeheads.net/showthread.php?t=8044

Not to contradict zebulon1, but Mark The Fixer and others have specified 512-KSC3503dstu TO-126 ecb 300v .1a 7W 150MHz 60-120hfe whenever replacing those pesky 1451s in Pioneer power amplifiers. I've rebuilt a SA-9100 and specifically used the 3503 for Q6 and Q7 on both power amplifier...

Best of luck with the SX-550. I have repaired several. Common problems are 1) the power switch contacts becoming worn and losing contact due to arcing, and 2) cold solder joints on the power supply transistors and often on the front panel pots, which solder to the main board. Let us know how...

Many have used Terry at http://www.terrysrubberrollers.com. No affiliation. He worked on a pair of rollers for my RT-909 and they look and perform like factory brand new.

No, I have not. But I have only worked on my personal PL-630. :) The general rule is to replace what is removed with the same value. There are reasons why the different value was used by the factory. Perhaps it was an engineering change mid run. Or there may be other components that are...

Walter, it's a fair question. I'm glad you asked, because I honestly didn't give much consideration to using tantalums. I'm not particularly smart about the specifics of their use in this circuit. Rather, I was following some blanket advice from a well-respected source of information at AK...

Thank you both for the words on the socket adapter. It may be some time before I complete the amps, but I will return to this thread and post my results.

Thank you for your replies. My main reason for asking is one of tube cost/availability. I've found the suppy of 6GH8A to be quite abundant and cheap, though I can understand that may not be the case outside of the US. I am aware that there are several options to replace the Mark III driver...

There are a couple of listings on that auction site for tube adapters to allow the use of 6GH8A in place of the 6AN8. Both tubes are listed as medium mu triode / sharp cutoff pentode. I'm currently using 6GH8A tubes to replace the 7199s in my Dynaco ST70 with very good results. Has anyone...