Hello i blew a transitor on my amp by fiddling with the bias screw
Marantz pm 17 ki signature.
Looking to replace but have no idea what I’m doing .
I’ve got a donner Marantz amp but different model and different numbers on them I need A 1303 but the donner has A1962 can I use this .
Thanks for any help
These are screwed to the heat sinks.
Marantz pm 17 ki signature.
Looking to replace but have no idea what I’m doing .
I’ve got a donner Marantz amp but different model and different numbers on them I need A 1303 but the donner has A1962 can I use this .
Thanks for any help
These are screwed to the heat sinks.
Hello thanks for the reply .
I’ve found a matched pair of transistors from China .
How would I know if there is anymore damage before I install the new ones.
Thanks Nath .
Check with a VOM the connections around the transistor under question. Very probably, a low Ω in the emitter (0Ω<R<1Ω), and around 100Ω resistor(s) at the base. Also, check the complementary pair.
In any case, when first firing the amp with the new device in place, use a current limited power supply. This is easily done using a filamentary (Incandescent, not led nor fluorescent) lamp in series with one of the supply lines, at first 60W lamp for 220V sets, with no load in the amp. (Output terminals open). If the lamps brights too much, switch it off immediately and review components. Lamps increases ohmic resistance quickly with temperature and power, so limits the current flowing into the DUT protecting from posterior damages.
If lamp appears to show no problem, still with it in series, check with a VOM for voltages at several points still without load.
If ok, then here you can test with load (Another lamp in place of the speakers).
In any case, when first firing the amp with the new device in place, use a current limited power supply. This is easily done using a filamentary (Incandescent, not led nor fluorescent) lamp in series with one of the supply lines, at first 60W lamp for 220V sets, with no load in the amp. (Output terminals open). If the lamps brights too much, switch it off immediately and review components. Lamps increases ohmic resistance quickly with temperature and power, so limits the current flowing into the DUT protecting from posterior damages.
If lamp appears to show no problem, still with it in series, check with a VOM for voltages at several points still without load.
If ok, then here you can test with load (Another lamp in place of the speakers).
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