In case of repair of vintage amp devices there is often a problem to find the associated replacement parts with right quality standard. This is particularly the case with many Japanese power devices - both BjT's and lateral MOSFET's.
One example is the Hitachi lateral MOSFET series mentioned above.
However, looking for devices as spare parts carriers only makes sense if they are not particularly popular - i. e. no collector's prices are being asked for them like on this model:
https://www.good-old-hifi.de/hitachi-hma-7500/
or
https://www.diyaudio.com/community/...r-amp-schematic-and-pcb-images-wanted.387093/
Therefore few populare amps like Harrison's K series are much more better for this aim, because in most cases such amps are faulty, because nobody is able to repair the potted hybram modules on ceramic PCB - check out
https://www.diyaudio.com/community/threads/harrison-type-k4000-k-4000-mkii-2x1000w-4ohm.147392/
and
https://en.audiofanzine.com/power-amplifier/harrison-information-technology-ltd/
I. e. such amps for Hitachi MOSFET's as spare parts are always cheap and one have a lot of genuine Hitachi's MOSFET power devices as NOS spare parts and no copies resp. counterfeits.
I assume, there are a lot of other not popular and thus not expensive PA mixer/keyboard/active loudspeaker power amp models equipped with such power MOSFET's.
Thank you for listing of such models.
Another option is to look for diy projects in used condition like Elektor's Crescendo or Mini-Crescendo
Unfortunately something like this is offered even more rarely despite the numerous diy projects that were described in the 80s and 90s in a lot of magazines.
Some URL's
https://www.diyaudio.com/community/...fier-for-diy-described-by-paul-kemble.220923/
https://www.diyaudio.com/community/threads/hitachi-mosfet-power-amplifier.127297/
https://www.diyaudio.com/community/threads/chinese-hitachi-mosfets.235479/
https://www.diyaudio.com/community/...t-driving-question-hitachi-amplifiers.192257/
https://www.diyaudio.com/community/threads/testing-hitachi-mosfets.41966/
https://www.diyaudio.com/community/...itachi-app-note-lateral-fet-amplifier.391700/
P.S.: The successor models from Exicon (fifth attachment) are probably less common than the Hitachi MOSFET's mentioned, making them even harder to find.
One example is the Hitachi lateral MOSFET series mentioned above.
However, looking for devices as spare parts carriers only makes sense if they are not particularly popular - i. e. no collector's prices are being asked for them like on this model:
https://www.good-old-hifi.de/hitachi-hma-7500/
or
https://www.diyaudio.com/community/...r-amp-schematic-and-pcb-images-wanted.387093/
Therefore few populare amps like Harrison's K series are much more better for this aim, because in most cases such amps are faulty, because nobody is able to repair the potted hybram modules on ceramic PCB - check out
https://www.diyaudio.com/community/threads/harrison-type-k4000-k-4000-mkii-2x1000w-4ohm.147392/
and
https://en.audiofanzine.com/power-amplifier/harrison-information-technology-ltd/
I. e. such amps for Hitachi MOSFET's as spare parts are always cheap and one have a lot of genuine Hitachi's MOSFET power devices as NOS spare parts and no copies resp. counterfeits.
I assume, there are a lot of other not popular and thus not expensive PA mixer/keyboard/active loudspeaker power amp models equipped with such power MOSFET's.
Thank you for listing of such models.
Another option is to look for diy projects in used condition like Elektor's Crescendo or Mini-Crescendo
Unfortunately something like this is offered even more rarely despite the numerous diy projects that were described in the 80s and 90s in a lot of magazines.
Some URL's
https://www.diyaudio.com/community/...fier-for-diy-described-by-paul-kemble.220923/
https://www.diyaudio.com/community/threads/hitachi-mosfet-power-amplifier.127297/
https://www.diyaudio.com/community/threads/chinese-hitachi-mosfets.235479/
https://www.diyaudio.com/community/...t-driving-question-hitachi-amplifiers.192257/
https://www.diyaudio.com/community/threads/testing-hitachi-mosfets.41966/
https://www.diyaudio.com/community/...itachi-app-note-lateral-fet-amplifier.391700/
P.S.: The successor models from Exicon (fifth attachment) are probably less common than the Hitachi MOSFET's mentioned, making them even harder to find.
Attachments
I understand your approach, however, for once I will not participate.
As very often, your threads start from a good intention but the problem is that we are not the only ones to read, and the information that you are going to give will increase the prices of devices that we still find at a decent price. .
to say, I have just found almost a complete page dedicated to you on the net and your research work is exposed there.
As very often, your threads start from a good intention but the problem is that we are not the only ones to read, and the information that you are going to give will increase the prices of devices that we still find at a decent price. .
to say, I have just found almost a complete page dedicated to you on the net and your research work is exposed there.
I don't think that the prices of the unpopular devices will increase noticeably because there aren't very many service technicians left who deal with the repair of old audio components. And there are fewer and fewer.
Furthermore, real collectors only drive up the prices for those devices of which very few were produced, such as this one under
https://www.diyaudio.com/community/...-motif-new-for-me-are-there-any-infos.244543/
but certainly not in the Harrison "K" series or similar amp models.
OTOH - if I don't start threads in this kind only extremely few service technicians would have this information, who would then of course call for significantly higher costs for their refurbishing work.
Furthermore, real collectors only drive up the prices for those devices of which very few were produced, such as this one under
https://www.diyaudio.com/community/...-motif-new-for-me-are-there-any-infos.244543/
but certainly not in the Harrison "K" series or similar amp models.
OTOH - if I don't start threads in this kind only extremely few service technicians would have this information, who would then of course call for significantly higher costs for their refurbishing work.
Last edited: