Technics RS1500US Erase Problem.

[uraldurusu]

Hello all, I am new in this forum and I need help for my Technics RS1500US. I have an erasing problem with the machine. When I erase the tape regardless of the tape brand (I have quantegy, RMG, and Ampex tapes) I can hear the un erased music when I turned the volume of the amplifier to loud levels. I cannot erase the recorded signal completely. I have the service manual but I don't know how to handle the problem. Any kind of help is appreciated.

Regards.

Ural Durusu

[uraldurusu]

I have fixed the problem. A service manual and a Multimeter is enough to overcome. If someone need detail information please ask me.

Regards.

[jcmusic]

Ok i am curious, what did you do?

Jay

[uraldurusu]

Ok. Page 31 of service manual talk about erase current. I thought that there should be a problem with the erase current. Technics says test the channels one by one and adjust them by using the same adjustment point and adjust the current to the desired value. Since there is only one adjustment point at the end I decided to adjust both of the channels at the same time. Also in the text Technics says measure voltage at point A and there is also a figure numbered as 38 showing the test equipment connection. In the figure test equipment is shown as connected to the point ER instead of point A. I 've connected the voltmeter to point ER but I can't read something similar written in the manual then I switch to the point A and this point was giving me similar V readings asTechnics says in the manual. Before adjustment/measurement: Line in level controls to minimum, tape speed selector to 38 position, set the rec mode selector on and put the unit into rec mode.

• Bias selector position 1: Value read on voltmeter is around 65mv so erase current is 65mA for the given formula. Adjustment point VR501
  
• Bias selector position 2: Value read on voltmeter is around 71mv.Adjustment point VR502.
  Bias selector position 3: Value read on voltmeter is around 78mv.Adjustment point VR503.

As a safety before touching to the adjustment points record the original Voltage readings for 3 bias positions for each channel Left and Right. If something goes wrong it is easy to go back. Here I don't have any Technics service so I did this trial and error job by using the service manual. I am a metallurgy engineer and I don't understand electronics can't change any parts by soldering etc. but I can measure and adjust things like this, so any kind of help is appreciated. If you think that I did something wrong please let me know. 2 months ago I have corrected my Nakamichi DRAGON s NAAC (nakamichi auto azimuth correction) problem by the help of WillyHermann Services.

Regards.

Ural

[jcmusic]

Ural,
If it is erasing now then you got it right imo.

Jay

[uraldurusu]

Yes it is erasing now. Do you have any suggestion to check also some other point?

Ural

[ironbut]

Nice going Ural! I guess you could spend a lot of money on other test equipment but if it sounds like it's erasing correctly, that's really all you need to know. My guess is that somewhere along the way, the former owner had the machine serviced by someone and like many techs will do, he/she just went by the measurements given in the service manual and called it good.
If it's wrong or confusing in the service manual, I bet there's a ton of machines out there that are adjusted incorrectly. Your post may become a classic in the RS1500 world!