a Greek catastrophe

[sakis]

MIG pro amplifiers ( MIG = made in greece ) existed before chinese war many clubs used them some of them were really products of excellent quality ( considering that made arround 1980-1990 ) but some others was a complete catastrophe ....

for the fun of it i ll give some pictures of a greek made catastrophe and may be some time in the feature i will be able to present some good ones

in the pictures please notice reasons for catastrophe and all the classical mistakes made

the circuit is something like the ET 480 or ETI 480 dont really remember that actually drives a pair of BD 139-140 for pre drivers that drive a pair of MJ15024-25 for drivers that drive 10 ( ten ) outputs MJ15024-25 ( that is a triple darligton ??? )

beyond a typical I limmiter no other protection
outputs are "wired" with any available cable
no soft start or output relay
5pair of MJ15024-025 work with only 2x10.000 mfd
inductor dumper is located inside the inductor
there is no "rail" to supply outputs
1R10W emmiter resistors ( ???? ) just to be on the safe side
no balanced input
ground is the box and thats it !!!
and of course vbe multiplier is located on the pcb and has no physical contact with the pcb
ventilator is too small and only injects fresh air inside the box but no where to come out ( no ventilation chanel )


now let us be kinda of fair ....this amplifier is constructed by a company that normally produces 100V amplifiers by that ... standards of quality for 100V speakers and installations ar fairly low it is not real hifi ... so they used the same pcb for a PA amplifier while using 10 pairs of MJ 15024-25 to produce arround 250 CR@@PY WATTS ... that of course is a waist of parts ...but its done to keep it on the safe side probably together with 1R10W emmiter resistors

of course if this amplifier is pushed to the edge will fail since the right side output transitor has the longest cable its too far away from the ventilator and the temperature is not controlled by anything

still ...this amplifier was never expected to work on the edge since it was originally designed for hoteling IE as a PA amplifier to work inside a hotel for a small party or a small bussines meeting ... made arround 1985 ...still working ...

amazing
enjoy the pictures

[jaycee]

Wow.. I have seen DIYers build better!!!

[sakis]

xmmm yes but was this arround 1980??? presumably not ... now that our standards hit the sky with badnwidth, power and slew rate wars ...some times it is nice to remember where and how it all started ...

regards sakis

[jaycee]

See the Leach Amp though, this was designed in the 70's and has excellent build quality (there were about 3 commercial versions of it).

[sakis]

true true ... you also may as well remember the japanese makes of the time that had non of these problems i think that at the time you could also find very nice either comercial or DIY machines ,,,

( is good also to remember that at the times greece was politically unstable had some oscillation ha ha ha ha resulting that till 1975 USA didnt supply much of technology here Just to be on the safe side )

[jaycee]

Ah, well I will blame my lack of knowlege on Greece on my youth... i was not born until 1980

[infinia]

I like the parallel 3X5A rectifiers the best. The triple follower is not that unusual, like Phase Linear,

[sakis]

it would be nice DIY though to trush the pcb and the rest keep only the outputs heat sink and may be trafo and rebuilt the all thing to a real amplifier ...but since this is not mine and belongs to a costumer i think it will be way to expensive to do

so it will have to stay as is

[indianajo]

Pardon my attemp at humor in advance. Most US academic track eighth grade students purchase and read a book called "Eight Great Greek Tragedies". Oedipus, Aeschelus etc. There are hundreds of these paperbacks in the charity resale shops. Now you have written the ninth Great Greek Tragedy. Sakis"s ninth!

[teemuk]

Looks like many generic SS amps from the early 1980's. Bad? Maybe, but then again we're likely spoiled by modern manufacturing standards.

If you open up any SS instrument amp from that era, chance is it looks way worse and quotes the same output power ratings with lesser heatsinking, fewer output transistors, smaller transformer and no fan at all.

Oh and...

...still working

pretty much sums it up.