Sigma Electronics Services

A few of my customers came and want me to sell their stuff, so here we go Sigma Electronics Christmas sale:
Pioneer SX-1280 receiver $4000
Nakamichi Dragon $4900
Pioneer RT-909 $ 2900
Golden Tube Audio SE-40 $740
Wadia 21 $950
More to come in the next days
I will not send out pictures, If you are seriously interested please come by and happy to run the unit and test. Sales are final, come with 30 days warranty. All units have been serviced by me at one point. No returns on the units. Questions will be answered if you phone me.

Latest fix for a big company. A valve had some problem with the ribbon cable connector, it came off the base. After repair, back to work as nothing happend !

Marantz 2500 in for full refurbishment including recap. Great sounding unnit after work done.

Volume inbalance in older Vintage amplifiers
I have been asked what's the reason the left or right side can be lauder in an audio system?
Cause could be because the volume potentiometers tolerance.
Logarithmic Potentiometer also called Audio-Volume Potentiometers mainly used for audio volume control to obtain a more natural linear-perception in sound intensity change when adjusting the volume, because the function of resistance versus angular displacement follows a logarithmic curve, As turn the shaft, the sound intensity seems to increase in a linear manner, even though the actual power variation is logarithmic. To compensate for the ears logarithmic behaviour, Audio Volume potentiometers were developed to improve it, While it is called logarithmic, it is actually an exponential curve. Because the human ear is sensitive to sound intensity in a logarithmic fashion, When running at low sound intensities a small change in intensity, It is perceived as a big change in volume, while at high intensities a large change is required for the same change in perceived volume.
Here is a datasheet for a stereo 100 Kohm potentiometer still made and sold: -tolerance is +/_ 20%
So measuring output can be different too !

I know Halloween just past but look at my December Horror Stories ! Have a good laugh ! Sadly some techs quality works come in for reworks.

Motor winding shop service call. PCB had a few problems with old capacitors and relays. Refurbished the circuit card, runs like new again.

Solid State Amplifier warmup times !
I found this interesting article on the web. Many people asked me about this subject already. So here is a professional opinion on this:
https://samplerateconverter.com/amplifier-warm-up?fbclid=IwY2xjawFrk8tleHRuA2FlbQIxMQABHVwxzmdwGAvB5SwFYlKerdIFkY9-7OQufVYnd58dZJlI968YJorm2j6lIw_aem_nQ99-R48N3AUrGLS79mKjw

Enjoy

Tip: About Amplifier "Warm-Up" Debunking the myth of amplifier warm-up: Learn about the concept of amplifier warm-up and how it affects sound quality in this informative article

Here is another monitor came in for repair and looking good after repair done.

Good way to troubleshoot circuit boards by comparing to a known good one and previously recorded on computer memory.

FADOS9F1 Circuit Board Tester Circuit Board Tester, Circuit Fault Finder for Repair

I got a new toy to help me with troubleshooting complex circuits
Check out the website for more info"

Mirage Rental Mirage rental is is the official distributor of Prot Ar-Ge products in Canada. We are specialized in cooperation with Sigma Electronic Services to help repairing circuit boards and provide diagnostic tools for service techs, including the famous FADOS system.