Hi,
I picked up a Luxman 1040 at the recycling dump yesterday, just before the guy was about to throw it in the skip. He was also junking a Marantz 2220 at the same time ! He gave them to me & I got both home. With some liberal deoxit cleaning & agitation of all knobs & buttons, both receivers work. Both of them even look very decent cosmetically. I was very happy with such unexpected luck & what a pair of beauties !
For the Luxman I wanted to check the idle current & DC offset as per the service manual. Actually the offset at the speaker terminals is already good (12mV & 16mV), but no matter how I turned the trim pots it makes no difference.
Same thing for the idle current which is across the F203 & F204 (fuses removed). Should be adjusted for 45mA, but I measure zero, with absoulutely no effect from twisting the trim pots. Same on a second DVM.
Am I missing something ? The amp sounds healthy and runs very cool. The bulb on the DBT quickly goes out & stays out.
Also the 2 light bulbs either side of the front panel are blown. They are 12V/70mA 5mm minature bulbs that press fit into a hole either side. I don't know where to source these bulbs, but I found some chinese sellers selling similar 12V/70mA bulbs pre-wired for model train enthusiasts. I don't know if they would be bright enough. Is there a led conversion I could consider ?
I picked up a Luxman 1040 at the recycling dump yesterday, just before the guy was about to throw it in the skip. He was also junking a Marantz 2220 at the same time ! He gave them to me & I got both home. With some liberal deoxit cleaning & agitation of all knobs & buttons, both receivers work. Both of them even look very decent cosmetically. I was very happy with such unexpected luck & what a pair of beauties !
For the Luxman I wanted to check the idle current & DC offset as per the service manual. Actually the offset at the speaker terminals is already good (12mV & 16mV), but no matter how I turned the trim pots it makes no difference.
Same thing for the idle current which is across the F203 & F204 (fuses removed). Should be adjusted for 45mA, but I measure zero, with absoulutely no effect from twisting the trim pots. Same on a second DVM.
Am I missing something ? The amp sounds healthy and runs very cool. The bulb on the DBT quickly goes out & stays out.
Also the 2 light bulbs either side of the front panel are blown. They are 12V/70mA 5mm minature bulbs that press fit into a hole either side. I don't know where to source these bulbs, but I found some chinese sellers selling similar 12V/70mA bulbs pre-wired for model train enthusiasts. I don't know if they would be bright enough. Is there a led conversion I could consider ?
Possibly..... unlike most idle current adjustments, this is actually measuring the current on the neg rail of each output stage , rather than the voltage developed across the usual emitter plate resistors....
Are you sure you are adjusting the correct pots? VR201 will adjust offset and VR202 is going to adjust idle current. When measuring offset, the meter needs to be connected across the speaker terminals and set to a mV range. When measuring idle current, the meter needs to be configured to read current.
My mistake : for the DC I thought the pot for the LHS speakers would be on the left & vice versa - no they were on opposite side to the speakers terminal ! For the idling current, I had my DVM set up wrong ! now everything is adjusted nicely.
I am really impressed by the build quality of this amp. Really nice components & cabinet. The tuner fantastically well . The TO3 output transistors aren't soldered in, but they clip into slots & held in by screws - really simple to remove !.
Now I know it works well, with no apparent mishaps (so far) apart form the bulbs , I can start thinking about recapping it.
I am really impressed by the build quality of this amp. Really nice components & cabinet. The tuner fantastically well . The TO3 output transistors aren't soldered in, but they clip into slots & held in by screws - really simple to remove !.
Now I know it works well, with no apparent mishaps (so far) apart form the bulbs , I can start thinking about recapping it.
Avoid turning it into a complete headache/scrapper
.... and re-cap section by section, retesting after each section is done.Quite common on amps/receivers of a certain era, not that soldered in were hard to replace in the first place even when soldered in, nor that they need to be that accessible in the product's lifetime either.
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