Hello everyone, i come across Parasound HCA-1200II amp,really like it but find out it has Toshiba 2SA1553 and 2SC4029 output transistors. In service manual, only one i have found and get from Parasound service (they said they don't know anything about this old amp..), output transistors are SanKen 2SA1386 and 2SC3519.
And BIG QUESTION, is there two variations of this amplifer in production or someone messed it up????
John Curl, everyone...help
And BIG QUESTION, is there two variations of this amplifer in production or someone messed it up????
John Curl, everyone...help
There was a few different versions of these amps. I've worked on one that had OnSemi outputs in it. I think they just built them with whatever they had available. They're a great sounding amp!
Hmm..
I am confused because this Toshiba and SanKen have different specs.. how you can use it in same circuit? And how to set amplifier curent without service manual for different transistors and probably other different elements??.....
There is only one service manual as I know
I am confused because this Toshiba and SanKen have different specs.. how you can use it in same circuit? And how to set amplifier curent without service manual for different transistors and probably other different elements??.....
There is only one service manual as I know
Most amplifiers are very tolerant to what output devices go in them. As long as the voltage rating and SOA aren't exceeded just about anything will work. In more modern amps the speed of the output devices can be an issue too. Negative feedback keeps everything working as it should. Input stage and VAS are more particular.
Bias current is pretty much the same for any output devices. 65mA / device is almost standard for BJTs with proper neat sinking
Bias current is pretty much the same for any output devices. 65mA / device is almost standard for BJTs with proper neat sinking
The supplies are +/- 70V if I recall correctly, so 140V + transistors work fine. Both of these devices are very fast (ft over 40MHz). Both have similar power ratings. Both are excellent devices and interchange perfectly.
Yes it's fast, but it is slower than that SanKen ones,does it have negative influence on amplifier stability and sound quality?? Parasound represented this amp and HCA-1500II (vitch have this Toshiba transistors as output devices in official service manual) as "50Mhz 15A output device" amplifiers. Is that statement suported by this data abouth Toshiba 2SA1553 and 2SC4029??
Attachments
Slower devices might cause shoot through (2MHz devices). All of these are fast enough not to worry about that.
Yes, maybe it's ok,but i would like someone confirm to me there was original/regular production of this amp with this Toshiba transistors,or someone with same configuration. I com across one old thread where someone has problem with different current reading from one channel, all 10 transistors given different values. Other channel was good. He posted table of reading with this Toshiba transistors, but that topic is closed
https://www.diyaudio.com/community/threads/hca-1200-ii-bias-and-output-relays.227313/
https://www.diyaudio.com/community/threads/hca-1200-ii-bias-and-output-relays.227313/
