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SPEC2 stays in protection after restoration

I noticed that the upgrade to the Spec-2 doesn't meet the levels of upgrades we already do to other models.


I would change meter board AWM-081 Q14 to a ksc2690 (512-ksc2690ays) - that transistor drives the protect relay .
:) On a bright note, there ALREADY is a flyback diode (D2) on the protect relay!!

Frankly the original design has :
2 reed relays (0.270 Watt each) being driven by the (q13) 2sc945
the protection relay (1 watt) being driven by a (q14) 2sc1384
and the protection light (8v 50mA 0.4 watts ) by (q15) 2sc1384.
I would take the Q14 that was freed up by this and put it in Q13's position.

Interestingly, I just realized that I have not yet done my "reverse engineering" on the Spec-2 for a parts upgrades list.
Thus in the last decade not even one has crossed my bench.
 
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Thank you Mark I will start ordering those parts, I have a second Spec 2 that I will eventually restore, you have been an invaluable help.
I have one last question; I don’t own an oscilloscope and therefore I can’t perform the current limiter sensitivity adjustment on the amp as stated in the service manual. Where should I leave VR2 and VR3 in the power amp boards pointing at to be safe?
 
Search for Velleman pcsgu250 on fleabay. That's what I use connected to a Windows 8 laptop. Has a built in function generator and dual trace scope (along with spectrum analyzer, transient recorder, bode plotter etc) If you are going to be doing repairs, well worth the small investment. Try to get one with probes included.
 
calavera68 said:
Thank you Mark I will start ordering those parts, I have a second Spec 2 that I will eventually restore, you have been an invaluable help.
I have one last question; I don’t own an oscilloscope and therefore I can’t perform the current limiter sensitivity adjustment on the amp as stated in the service manual. Where should I leave VR2 and VR3 in the power amp boards pointing at to be safe?
Click to expand...

That's a hard answer, that I can only take a guess at. (granted - it's a Mr. Spock guess, but still a guess)

And I cannot trust the definitions of CCW or CW.

So, from the center tap of the pot (VR2 or VR3) , each should be adjusted for 0 ohms TO the closest thermistor (TH1 or TH2) to it.
VR2 & TH1 (plus side of the waveform to ground)
VR3 & TH2 (minus side of the waveform to ground)

That SHOULD minimize the effect of the power limiters.
 
markthefixer said:
I noticed that the upgrade to the Spec-2 doesn't meet the levels of upgrades we already do to other models.


I would change meter board AWM-081 Q14 to a ksc2690 (512-ksc2690ays) - that transistor drives the protect relay .
:) On a bright note, there ALREADY is a flyback diode (D2) on the protect relay!!

Frankly the original design has :
2 reed relays (0.270 Watt each) being driven by the (q13) 2sc945
the protection relay (1 watt) being driven by a (q14) 2sc1384
and the protection light (8v 50mA 0.4 watts ) by (q15) 2sc1384.
I would take the Q14 that was freed up by this and put it in Q13's position.

Interestingly, I just realized that I have not yet done my "reverse engineering" on the Spec-2 for a parts upgrades list.
Thus in the last decade not even one has crossed my bench.
Click to expand...
A parts upgrade list would be very interesting....
 
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