Photos of my restoration

[binary]

Hello,
I would like to show you some photos of my M166 Gradient Amp (Brazilian brand). I bought this amp used with several problems and very dirty and I made the total restoration. I even changed the VU Leds to white and blue.

Fell free in give your comments.

Regards,
Julio.

[binary]

a 2nd photo:

[lineup]

You did a good job.
Nice front with new VU-meter LEDs.

Did you replace many components?

[destroyer X]

This is the best amplifier made in the eighties, one of the best we have made in this country.... it is one of the five best ones.

Este amplificador é excelente, eu adoro a sonoridade dêle, e você fez um belo trabalho, parabéns.

regards,

Carlos

[destroyer X]

I think i have not, but finding the schematic, i will produce two channels to listen them once again, as it produces a very soft bass and beautifull voices.

The top high frequencies seems a little bit mufled to me...but this is something we can arrange inside the circuit caps, installing better tweeter or arranging speaker crossover.... seems to me, this is personal, subjective feelings...my own evaluation.

Thank you for publish our things here.

regards,

Carlos

[lineup]

76- Quais os transistores originais, de estágio final,
dos amplificadores Gradiente M-166, M-246, M-366 e receivers M-1560 e M-1660?

Amplificadores Super-A
M-166: Toshiba 2SA-1146 e 2SC-2706
M-246: Toshiba 2SA-1094 e 2SC-2564
M-366: Toshiba 2SA-1095 e 2SC-2565
Receivers Super-A
M-1560: Toshiba 2SA-1094 e 2SC-2564
M-1660: Toshiba 2SA-1094 e 2SC-2564

57- A substituição de um transistor Toshiba por um Sanken em um amplificador Super-A, da Gradiente, melhora o aparelho?

Não há qualquer embasamento técnico nesta afirmação, sendo que não se deve substituir transistores ou quaisquer componentes indiscriminadamente. Toshiba e Sanken fabricam componentes de alta qualidade. Não é a marca o mais importante, mas, a característica de compatibilidade do componente.
Poucos transistores da Sanken são adequados para os amplificadores Super-A, da Gradiente. Utilizar um transistor inadequado, no 166, 246 ou 366, resulta em desempenho e confiabilidade inferior.

http://www.geocities.com/fabiomauriciotimi/faq.htm

I get the original output stage transistors for M-166 are:
Toshiba 2SA-1146 and 2SC-2706

[binary]

Thanks man.
The basically the restoration was made followings steps:
-The chassis was completely disassembled
-All parts, were cleaned one by one, several metal parts were washed with soap.
-All cables were replaced
-Several screws were replaced.
-The pcbs were washed with isopropylic alcohol and applied the protective resin
-Several small electrolytics were replaced.
-Volume potentiometer replaced.
-The electrolytic of power supply filter were replaced from 2 x 4700uF by 2 x 10.000uF.
-The pair output transistors of 1 channel were replaced by originals
-Reactivation of Super A circuitry
-The original VU led were green, yellow and red, so I decided to change the leds by new ones, with color white and blue.
-The VU window, knobs and pannel were polite.
-And some other things.

Yes, it was a lot of work, actually 3 weeks, working on weekends or at night after the work. But the result was a prize. Beautiful, clear and “warm” sound, punch bass.
It has aprox 90WRMS (8ohms) total power output, but sounds like a 200WRMS amp.

Note: Below is the photo of pcb power amp before assembly. Here is an enhancement: the Super A bias transistors were glued with epoxy in an aluminum base and assembled to heat sink. I had to do this because the original solution was very poor.
Regards,
Julio.

[Tekko]

How does it sound ? Looks well built, but very small heatsinks in my eyes.

[binary]

It has 42WRMS per channel in 8ohms or 60WRMS in 4ohms.
The rails voltages are -37v +37v with load.
The amp weights 6.2kg.

The heat sink is divided in 2 parts. One is assembled on pcb and the main part is assembled on chassis. On below photo you can see it.

[destroyer X]

Very good work, and very good amplifier, sounds very nice....a precious unit...take care of it, there's a lot of guys searching for this model in used shops.

Very well constructed, small, ligthweigth, heavy sound, slim line, good range on controls...very nice.

Este som é muito legal.

Carlos