hi Perry
just an update on this amp, to make it look pretty, i measured all the daisy chains and replaced with 1% single resistors, power supply was fully functional.
i sourced TIP35/36 output transistors and fitted to the board, i figured the audio driver section has some really powerfull drivers so driving the hefty TIP35/36's wouldnt be any trouble.
the amp has has achieved full operation. i havent bench/endurance tested this amp yet.
the power inputs and speaker outputs standard with this amplifier are just wires popping out thru holes in both side plates. im am going to strip terminals off a donor board, and after milling out calculated slots in the side plates, fit them to this amp, pending which i will bench/endurance test it to full power.
just an update on this amp, to make it look pretty, i measured all the daisy chains and replaced with 1% single resistors, power supply was fully functional.
i sourced TIP35/36 output transistors and fitted to the board, i figured the audio driver section has some really powerfull drivers so driving the hefty TIP35/36's wouldnt be any trouble.
the amp has has achieved full operation. i havent bench/endurance tested this amp yet.
the power inputs and speaker outputs standard with this amplifier are just wires popping out thru holes in both side plates. im am going to strip terminals off a donor board, and after milling out calculated slots in the side plates, fit them to this amp, pending which i will bench/endurance test it to full power.
Hi Perry
thanks for the tip Perry
the came in with an assortment BJT's in out output section, i mean like yes all NPN in the NPN banks and all PNP in the PNP banks BUT, in one bank i had a Cxxx with a Dxxx with a tip35c, all NPN but different parts altogether. all banks had this problem.
it was almost as tho a previous tech had no clue what he was doing, i seriously doubt that this amp came from factory like that.
of all the BJT's, the TIP35/36's seemed to have the original solder on the legs, assuming this repair tech hadnt touched these BJT's, i assumed them for originals.
i seriously doubt that a tech that could sub different NPN BJT's in the same bank could all of a sudden solder like a master for a few legs lol.
adding to my suspicion that the TIP's where the original BJT's, was the fact that they where extremely old package type. i have only seen that package type in 20+ year old amps. its unlike the TO-247 or TO-3PN packages we see today. its sort of exactly like TO-220 but just bigger. the other mix of BJT's where of the newer package types TO-247 and TO-3PN.
seeing as this amp is from that 20+ year ago era...
but none the less, i will heed your advice and monitor current draw Perry.
the amp doesnt really heat up at idle so i will drive a sine signal into it, load the channels and monitor the current draw in the coming days.
thanks for the tip Perry
the came in with an assortment BJT's in out output section, i mean like yes all NPN in the NPN banks and all PNP in the PNP banks BUT, in one bank i had a Cxxx with a Dxxx with a tip35c, all NPN but different parts altogether. all banks had this problem.
it was almost as tho a previous tech had no clue what he was doing, i seriously doubt that this amp came from factory like that.
of all the BJT's, the TIP35/36's seemed to have the original solder on the legs, assuming this repair tech hadnt touched these BJT's, i assumed them for originals.
i seriously doubt that a tech that could sub different NPN BJT's in the same bank could all of a sudden solder like a master for a few legs lol.
adding to my suspicion that the TIP's where the original BJT's, was the fact that they where extremely old package type. i have only seen that package type in 20+ year old amps. its unlike the TO-247 or TO-3PN packages we see today. its sort of exactly like TO-220 but just bigger. the other mix of BJT's where of the newer package types TO-247 and TO-3PN.
seeing as this amp is from that 20+ year ago era...
but none the less, i will heed your advice and monitor current draw Perry.
the amp doesnt really heat up at idle so i will drive a sine signal into it, load the channels and monitor the current draw in the coming days.
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When testing an amp like this that you may question the bias circuit, you need to drive it until it goes into thermal protection. You can do this with music with a lighter than the lowest rated load. If it's taking too long to heat up, throw a towel over it to prevent it from cooling.
The TO-218 package didn't go obsolete that long ago. They just stopped selling them a few years ago.
The TO-218 package didn't go obsolete that long ago. They just stopped selling them a few years ago.
yes this is correct TO-218 package! ok i didnt realise they were available until recently.
bench/endurance testing previous Class AB amps, i usually hit thermal throttling 20mins into the test, BUT the test however is quite stressful. i feed it with a 10hz sine, adjust the gain to just under/at clip and the amps where loaded at rated lowest impedance.
what is the downside to testing at these conditions perry?
i must admit, after thermal throttling and recovery a few times at those test parameters, i felt very confident that the repair was bullet proof.
bench/endurance testing previous Class AB amps, i usually hit thermal throttling 20mins into the test, BUT the test however is quite stressful. i feed it with a 10hz sine, adjust the gain to just under/at clip and the amps where loaded at rated lowest impedance.
what is the downside to testing at these conditions perry?
i must admit, after thermal throttling and recovery a few times at those test parameters, i felt very confident that the repair was bullet proof.
That's an OK way to test. I test with music driven into intermittent clipping. This allows me to listen for the amp to do strange things. I don't listen at full volume unless I really feel like listening to it. I tap off of the dummy load with an incandescent lamp in series with a full range speaker (Equipment page, item #9). The lamp limits the output quite a bit. The wattage of the bulb and the impedance of the speaker determine the actually limiting.
you know perry, judging from all the help i got from your ART, im actually going to investigate this setup.
currently, i have a coil ripped from nonfunctional sub woofer, the sub woofer had rubber surround damage and hence quite a bit of coil rub. i pulled the coil just in time to salvage it. when bench testing, i currently submerge it in water to dissipate the heat.
my next step was to turn a chunk of aluminium that would snug fit into the bobbin, drill channels into it, and cool it with liquid/radiator cooling. but i think going that far, i might just source some enamel coated copper wire and wrap my own wire resistors around a custom chunk of aluminium.
but before all that, im going to check out your ART
currently, i have a coil ripped from nonfunctional sub woofer, the sub woofer had rubber surround damage and hence quite a bit of coil rub. i pulled the coil just in time to salvage it. when bench testing, i currently submerge it in water to dissipate the heat.
my next step was to turn a chunk of aluminium that would snug fit into the bobbin, drill channels into it, and cool it with liquid/radiator cooling. but i think going that far, i might just source some enamel coated copper wire and wrap my own wire resistors around a custom chunk of aluminium.
but before all that, im going to check out your ART
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