bias

Dear all, I inherited a TA-4650 from my dad which had been idle for around 15 years. I used it with great enjoyment for more or less a year before noticing one of the channels was sounding more silent than the other. The difference wasn’t huge, but it was perceptible. Given the reputation of...

Hi from Sweden, My name is Christian. I'm new to posting here, but have been reading for a few years while fixing a few receivers. No major repair, mainly recapping and cleaning. Recently I picked up a receiver: Expert TA 940, which is built by Superscope and is the same as model R-1240...

Hi everyone, I recently picked up a Yamaha CR-800 for $150 as a non-working unit. When I opened it up, I found two blown fuses. After replacing them and testing with a dim bulb tester, I discovered one of the output transistors was shorted. I decided to replace all four outputs with new ON...

Hey guys. I have a 2325 that I re-capped a few years ago. Sounds fantastic hooked up to my AR-11's............. I have three issues, some of which I hope you lot might be able to comment on: 1) It's recently starting to hum across both channels. I pulled the lid and checked the PS: spot on...

Hello, does anyone have the manual for either the Project One Mark 1500, or Telefunken TR-1500 DC?

Hello and Good Day/Afternoon/Evening to everyone so my father has this Aiwa SA-P50H that he bought a few years ago and its all original but has an issue, sound comes out distorted (mostly on one channel, the other one its almost indistinguishable but its there) going by memory so the amp...

i have a music angel 845 mk3 , and do not know how to adjust bias. what tools , where is the specific screw?

Hi guys, As the title says, the amp has DC Offset and I don't know the cause, so I'm publishing this post, hoping that someone can help me, because I've run out of ideas (also quite frustrated :/ ) A little context ... I have had this pioneer sa-7500ii for a few months now and it originally...

Hi all I recently got a 771 receiver in lovely condition purchased as not working. I’ve given it an overhaul which included Recap Replace 2sa726 with 2sa970 Replace 2sc1313 with ksc1815 Replace all zeners Replaced trim pots Replaced 2sc1364 with ksc2690 Relay clicks out as normal with a 70w...

Dear All, My Sansui B2101 suddenly stopped producing sound. The display bars works, meaning peak levels up and down with a pre input. I have checked all the outputs are fine. About 300mV is in the speaker terminals. I checked the DC offset (see SM attached image) and have found that DC voltage...

Dear friends, There is a defect in my Teac A-3300SX: 100 kHz in the left channel on the line output. The monitor is in Tape mode, Record is on, the VU meter in the left channel is deflected to the left and can be changed with the Output knob. I've been trying to locate the problem for a long...

Hello! I'm having some issues with a Marantz 2250. Specifically the H005/H006 (HV0000212). Broken lead on original part. I'm seeing more than a few fixes on the internet, but without confirmation, I'm worried I'll blow a output transistor. Currently I have two 1N4007 diodes in series attached...

Hello guys, I need your assistance once again. I bought a yamaha cr-420 for dirt cheap. Symptoms - distortion in left channel. I was surprised it worked flawlessly for like half an hour. Then it started to act up. Well, this was't the only problem. Right channel bias couldn't be adjusted. I...

Hello all and thanks in advance I recently purchased a beautiful pair of Luxman MB3045 amps. They are running well but given the age and the previous history being unknown I would like to check the bias etc on them. I have done a bit of a search online and thought I would come across a service...

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...