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    Sony TA 5650 preamp humming

    I finished working my way through a TA 5650 which is now dialed in and functional but im getting a hum noise from the preamp. The amplifier stage is dead quiet but when the pre is connected the noise is there. It doesn't seem to be affected by any particular source or controls although I do get...
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    Sony TA-4650 voltage issue...need help!

    I am have a tough time trying to pinpoint the issue with my Sony TA-4650. The unit has some funky voltage on the left channel and I was hoping someone might be able to offer some guidance. I took a snip of the service manual and inserted the voltage which are causing the issue. All 4 Vfet...
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    B2 burning fuses (F203-F204)

    My beloved B2 is once again down for an unknown issue. Afew weeks ago the unit went silent, I immediately shut it down for evaluation and found the F203 was open. The fuse was the original and it looked to me more like if cracked than "blew" so I changed it and all was well. Yesterday she went...
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    Sony TA-4650 voltage trouble (Vfet gate)

    Im working my way through another 4650 and have run into an issue. Currently the unit is all back together (minus Vfet) as I wanted to confirm voltages before installing them. Everything seems good in the right channel but the left has some odd voltages at the (Gate) Vfet sockets. The source...
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    B2 DC offset fluctuation

    After a recent "scare event" in the left channel of my B2 I decided to go ahead and finish the restoration that I started awhile back. The driver boards had already been recapped but I did not change out any of the transistors as I was trying to keep it as original as possible. After reading...
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    C2x transformer replacement (100v to 120v conversion)

    Just putting the finishing touches on my C2x project and thought I might as well throw up another C2x post. There seems to alot of these getting worked on lately which is nice to see. Anyways the transformer conversion turned out to be a success. If I did it again I would make afew changes to my...
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    C2x running hot (continuation)

    For anyone who has read through the "C2a vs C2x" post this is a continuation of it with an issue that was discussed in that thread. For anyone who hasn't it was discovered than my C2x runs at a much higher temp than the C2a. The temp seemed to be located on the left side which made the likely...
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    C2a MC head amp issues

    I had taken my c2a out of duty for the last few months due to an issue in the MC head amp. I had afew other preamps to test out so it wasn't time sensitive to do the repair but it't time on the bench has come around. The problem is speaker popping/crackling in the right channel...although its...
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    B2 bliss

    Finally had a chance to get my B2 back in the main system. I had pulled it out months ago to install a new front switch assembly, main filter cap board (courtesy of Mr. Rottalpha) and main filter caps and left it on the shelf after that as I was rotating some other item through for testing...
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    Sony TA-E86 Bass Boost Delete

    I want to eliminate the bass boost output on my TA-E86 and was thinking about doing the following. Green items will be pulled and the Blue circle I will just bridge. The second output will be used for a powered sub but I do not want the extra boost from the preamp.
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    Sony TA-N902 Class A?

    Recently took possession of a Sony TA-N902 and was wondering about it's specs. Everything I have read (not much info out there) indicates that it is 130w/channel in class A. Perhaps it has a more intelligent design than other class A amplifiers I have worked on but with a bias setting of 50mV...
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    Sony TA-N86 no bias in left channel

    Finally getting this thing back on the bench and was checking to see if any experts on these things had some advice to share. I have no bias current in the left channel. The unit has has the power supply gone over and the rest of the amp recapped. I have checked almost every component on the...
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    Kenwood L-07cii preamp capacitor substitute question

    I'm working my way through a Kenwood L-07cii preamp and had a question about a capacitor substitution and how it may or may not affect the unit. There is an bi-polar electrolytic capacitor at the output of each phono stage (left and right channel of MM and MC) which is 15uf 50v. After that cap...
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    Sony TA-N86 voltage issues in left channel

    I've been fighting my way through repairing my TA-N86 without much luck and was hoping for some assistance. The bias in the left channel is incorrect and I am struggling to figure out why. The voltage on the collector of Q105 is low but the weird thing is that it changes if I put my hand on the...
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    Sony TA-N86 schematic?

    Wondering if anyone has the schematic for the Japanese version (non B) TAN-86? I'm struggle with an issue and it would be helpful to have the correct schematic. The TAN-86b one is close but there are some differences. Thank you
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    Sony TA-N86 left channel issue

    I have been working through my TA-N86 100v amplifier and am stuck on a problem that I cannot seem to figure out. The left channel is not working and I think that I have narrowed it down to a certain below pictured below. All voltages read normal with the exception of the Q124 collector which...
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    Yamaha B3 volume potentiometers

    I've been working through the latest project and have come across an issue that may or may not require attention. The volume pots are similar to the ones found on the B2 except they have a nice detent feature so I would like to keep them if possible. The other difference is that they are double...
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    C2a vs C2x

    I'll start by saying that I have probably read every testimony I could find on both the C2a and C2x control amplifiers. I have been happily using my restored C2a for almost a year and can confidently say it is the best control/preamp I have heard to date. I switch between a B2 and L-07M's for...
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    Sony TA-4650 mystery pre-amp noise

    I have a TA-4650 that seems to have developed a strange issue. When I feed a signal directly into the power amp everything is normal and sounds great. When I feed the signal through the pre amp it I get a re-occuring static/buzz/popping noise (in that order) in both channels. It seems to occur...
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    B2 meter board voltage issue

    Im working my way through another B2 and have stumbled upon an issue in the meter board. When the amp arrived the meters were acting up. I finished a complete restoration of the amp and all seemed well but the meters are still not acting normally. The meter board outputs around 125mv to the...
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    L-07cii service manual?

    Wondering if anybody has a copy of the L-07cii service manual they wouldn't mind sharing? I have the L-07c service manual but there are quite afew differences internally. I have not been able to find a source for it online
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    B2 PSU capacitor question (ordered the wrong caps)

    Im working my way through the PSU on my latest B2 job and realized that I made a mistake when ordering caps. Instead of the 50v 10uf BP caps (C227/C228) I ordered 50v 100uf BP caps. I was wondering if there might be a downside to installing the larger caps in this location? I really would prefer...
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    L-07Cii adding second preout

    I have been listening to my L-07M power amps for the last month or so and have been very impressed by them. So much so that I decided to track down a L-07Cii pre-amp to see what effect it will have on the sound. I am currently using a Yamaha C2a which by my ear is a fantastic control amplifier...
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    Sunfire HDS-8 amp transistor identification help

    I am working on my HDS-8 subwoofer and have narrowed the problem down to the standby board. The issue is that the sub will not switch on. I found afew charred resistors which I have replaced and one bad transistor. The TO-92 transistor reads M SD 13003 I ordered what I thought would be a...
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    L-07M remote switch options

    I am going to try out a pair of L series monoblocks and am just thinking out how I want to use them while they are in transit. I will be using my C2a to feed them as budget does not allow tracking down a L-07C variant and Im sure the C2a is up to the task. After digging around I saw mention on...
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