Most of these home devices have a weak power supply. Sometimes this contains amplification channels of different power and circuit.
Radiators have insufficient surface area.
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I have dismantled several of these 5x65W multimedia contraptions and recycled their transformers and heatsinks to build decent quality stereo amps with pairs of Elliott's P101, notably.
Maybe so, but Elliott´s P101 requires +/-70V rails to put out rated 180W, I very much doubt those "5 x 65W" amps use much more than +/- 35V, if that much.
Fed from those rails, powerful P101 become plain vanilla 60-ish power amps, not bad but nothing to brag about.
Of course, driving an humble pair of 60W amps is an easy peasy job for original transformers.
+/-72 V is a whole lot more realistic than +/-81 at this power level, and especially with just an EF2. Probably within the capability of the drivers you have now - the S/B breakpoint is under 40, so 80 volt supply is iffy. I’d still upgrade the stock heat sinks, unless they are sharing the output heat sink already because full-pack TO-220’s are already at a disadvantage compared to the bare tab versions.
Those 5x65 POS’s probably use +/-50 or 55 volt supplies and drop like a stone.
Those 5x65 POS’s probably use +/-50 or 55 volt supplies and drop like a stone.
Thank you so much for the excel ! Its people like you that make this forum so much better. I have learnt a lot here... Again much appreciated, both you Olddiy and Wg_ski
The drivers are indeed plastic over metal types, they had no heatsinking... so I installed smallish clip on heatsinks that almost triple the radiating area. I have a 65C thermal breaker also installed on the outputs that cuts out the input signal if the sinks go over 65c. Also replaced the 4.7uF input electrolytic cap with a PP film type. Sounds more open and less constrained. Thanks again for your help and thoughts!
Already done this for a couple of receivers... one got fitted with amp modules form Sonance, bridged gives me about 300w/8e stereo. Used a larger Onkyo DS-696 chassis for this and forced air cooling. The transformers were 2 from similiar sized Kenwood M1A (with those IC outputs), so its a dual mono set-up. The other one was fitting a Chinese A60 kit into a Rotel RSP-1056 receiver chassis, this runs the mids / highs on my PC speakers, the former runs the 8" subs for it... I got these KM-206's at a decent price hence wanting to up the power and use them as HF amplifiers in my Home theatre.
Thanks for appreciation, hope some moderator sees this; my posts are delayed (I think hours ?), invisible until a moderator see and approves them: "After a few quality posts you will be able to post freely" not as encouraging as intended...
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Hey Guys: for the second unit, since I have options, I think considering leaving the Sanken outputs (2sa1216/c2922) in there, and running them from one channel's driver like we did before with one exception (I will give my reasons later), I'd like to convert this to an EF3 from the existing EF2. So I will insert "super" drivers ahead of the existing drivers (which then become pre-drivers), these would feed the Sanken outputs. The question is what drivers... I have a few 2sb817/D1047's lying around that could be used. The pros are, they are free to me, they are smallish in size, they have good gain linearity (even at 5A they are over 50hfe ), they have been used as drivers in the Adcom GFA-555ii power amp which has rails of +/-84vdc , they also have a cob of 150pf which is easier to drive. The only con I see is the vce of 140v which makes is close to the Peak rails of 144vdc (+/-72v) in the KM-206 , however they worked just fine in the Adcom with +/-84v rails. They just used a 33ohm emitter resistor across to load them. Do you guys the same could be used ie. Adding drivers 2sb817/2sc1047 with 33R on their emitters?
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I might consider building some “modules” with two Sanken pair with emitter resistors and the D1047/B817 drivers on them, and wiring the whole works to the main PCB, driven by the existing drivers. It might be less of a kluge. Making your own STK Darlington Power Packs out of real transistors.
In Reality, I am just lifting the bases off the existing outputs and feeding them from the new drivers from a build/ install perspective. The Sanken's ER's can remain installed as is, this helps me use the existing LED outputs as well since they are already wired to the outputs today, and also the speaker switches on the front panel. It will be a kludge either way.
I am curious though, do u have a schematic on these power packs you refer to?