bias

Hey! I'm getting a wondering bias voltage across pins J708 & J710 (bias voltage). Its causing some annoying static and I'm not sure where I should look first. The unit has been re-capped and sounds great for the first hour, but eventually the bias fluctuates on the left channel and it throws the...

Hello! I recapped a marantz 2250 and it's looking really good. However, I'm getting some wandering bias voltage on one channel. Testing at points J710 and J708, one channel has a steady 8mA. The other channel however wonders all over the place & it creates a static over the speakers when...

This subject has been discussed so many times, but I still didn’t find some kind of a ONE-Pager with all pins and millivoltage settings from an official Pioneer Service Manual. Has anyone from this forum got ALL information or can help identify the correct pins to measure DC Offset and BIAS?

Hello to everyone, I have a problem with my SA-606 (SA-6700 version for Europe): There is an hiss similar to white noise through the headphone output. In the past I did some maintenance: 1) Recapping - used Nichicon "audio grade" KA series (light blue sleeve) for everything but main filters...

(moved to Pioneer audio - my bad)

Hello everyone I am currently restoring an AU-555A and facing an issue with the left channel of F1266 power board. In brief I have replaced all electrolytic caps, all transistors except the C1030, still good. I have individually checked all resistors, pots and conductivity of all copper traces...

More than a year ago I restored a Sansui AU-517 with a lot of help from Sansui specialist here on AK. It is still working fine. A few months ago, I was able to get one for myself, as an upgrade from my Sansui AU-217. It played OK, but not super. This was expected since it is more than 45 years...

Here are some tips which you might find useful when you have a bias problem. Below is a schematic snip of a driver board for an AU-517. TR06 (centre left) is the bias control transistor, just below it is VR03 the bias trimmer, the transistor and the trimmer are vital to the operation of the...

Hello Folks, I found a BA-2000 at a thrift store and was trying to restore it. I swapped all fuse resistors, relays, and caps. It took me a month to do all this. I was excited about finally using it with my JBL's but when I tried to adjust the bias, C37 on F-2661 blew open. My Mistake was...

Hello! I recaped a 790 sansui, don't working before recap. Now relay clicks, DBT show no shortcut, unit sounds Bad and once the volumen reaches 35-40%, distorsion is really Bad and finally relays click and sound go out. Dc offset is ok, about 3+5 mv, but bias is 45V!!!! On test point 5-6 & 5-7...

Hi all, I have changed all the transistors on the F-2518 Driver Boards and everything seems to work fine, at least on the left channel. I am able to adjust the bias on either board on the left channel, but the right channel reads 0 mv on both boards. To me, that means that both of the boards...

Trying to wrap up a refurb of an SX-890 and can't get one channel to bias (DC Balance) and it won't get out of protection. At one point it would get out of protection but wasn't stable on on either channel when trying to DC Balance At this point, on the Right Channel I get ~ -35V at pin 12 and...

I have no Bias on Right channel when I measure across R71/R77? I get some audio but it's distorted. Left channel is fine. Audio is clear in headphones until I put an 8ohm load the right channel. I have checked all the resistors around the driver section and the 2 driver transistors look good...

Hello all, Thank you to all the members, both seekers and helpers, who make this website a living reference for hifi and audio related care. I just bought a Technics SU-8088 in its original state, no revisions or repairs done (supposedly, ever). I tried it with headphones, played 3 or 4 songs...

I bought a SAE 2400L this week for 350. It was in “working” order but I figured it would probably need an overhaul before use. Got it on my bench today and channel B seems great. Was able to get the offset and quiescent dead on. (Don’t have a distortion analyzer to check bias unfortunately)...

It's been a long journey with this 6060, mostly centered around the 2647 Driver board. After replacing the 2SA726 Transistors and a recap of that board, I get clear sound on all inputs from both channels and the bias on both sides adjusts to in spec per the service manual. I'm not sure if the...

Is there a typo in the manual? I have looked multiple times can’t locate R47

Hi, I'm trying to find out why the bias on both channels can't be adjusted. The amp was recaped, I cleaned the relays which work fine (the first clicks within one second after powering up, followed by the second relay (which turns the VU lights on) 3 seconds after). The voltages going to both...

The receiver is in protection, speaker relays do not click on. Was testing DC offset at terminal 27 and 28 and am getting -2.5vdc tried to adjust it on driver boards but would only get down to -2.2 Vdc I’m at a loss as to what it could be. Any help would be much appreciated

Greetings fellow Ak'ers! This puzzle has me stumped - any good puzzle solvers out there wanna try it? I have rebuilt a Kenwood KA-3500 amp with a full recap, many transistors, resistors and diodes, and new Bournes trimmers, too. This is my 12th recap of this model, but I'm stumped. The Left...

OnSemi finally did what so many have suggested and put a matched bias diode junction in the same case as the output transistor. They call them ThermalTrak and is a 5-pin TO-264 case. No more bias lag issues. I will have to try these out. Datasheet attached.

Left channel is steady at 35mv Right channel went from 75mv to 98mv Right channel produces a disgusting buzz/humm through the right speaker that is constant no matter the amount of attenuation. Needless to say that it's in need of repair, that's a given. I'd just like to know if these...

I picked up a Quadraflex 180r today cheap, it had a noisy transistor on the right channel which I replaced, but I can't find any information on how to check and set the bias, any info would be appreciated. I also noticed the lamps are dim, I measured 8vac on the line, can anyone confirm what the...

This subject has been discussed so many times, but there is one information missing I like to find the answer. Every reply covering DC Offset and BIAS points to a millivoltage range with 20mVDC for Bias and DC Offset close to 0 mVDC. BUT sometimes it’s very hard to get the DC Offset close to 0...

Does anybody have the adjustment procedure for this receiver ?? I have a service manual but it doesn’t show how to set the offset or bias current. Any help would be appreciated. I just got this receiver and fixed a couple of issues. The headphone jack was giving me issues with the L...