Beautiful receiver, you don't see many of these in the wild anymore. This unit looks to be in great cosmetic condition; your customer will be very happy. Thank you for your time.
I have found that removing the silver oxide (black stuff) from switch contacts does just want you said, you can end up removing all of the silver from polishing. Instead, I put the part in a table salt bath with some aluminum foil. When the silver part touches the foil the oxide almost instantly converts back to silver. This retains the sliver on the part. Be sure to degrease the part completely. For small parts I spray a couple of oz of Brake Clean into a plastic Rx bottle or Zip-Loc bag along with the part. Shaking it should do the job. If not set the bottle or bag in a water bath in a ultrasonic cleaner. A short ride there will degrease the part. Then give it the short bath in NaCl / H2o with the foil. Great results without sacrificing Q-Tips.
Pretty sure that Dynaharmony refers to the Class G amp circuitry in the BEAST. Love my Hitachi's...two SR-903's, 1 SR-804, and 1 SR-503L. The Monster SR-2004 is quite the find...although the 903's pack more than enough power (75W, with 160W peak power) for my needs. Hitachi's are generally under-rated insofar as brand recognition. It terms of build quality...exceptional. In terms of sound quality...I certainly like Hitachi sound. Note, Hitachi was a key supplier of component parts to all of the major audio equipment brands during the mid to late 70's.
I was hoping to see a date code but couldn't, I don't think I've seen that monster before. I remember the Pioneer receivers from friends houses and a couple of others like Sansui or Toshiba, they were always the owners pride and joy and we were never allowed near them ! Surprised to see plastic insulators behind the transistors, plastic does not conduct heat very well so I wonder how many of those amps had plastic insulators that resulted in the amps being binned ?
Nice work Trevor, but I wouldn't change active devices that don't match spec or meet minimums. Transistors 2SC1213 Ic=500mA whereas 2sc2240 Ic=100mA. Chasing a problem that wasn't there initially. That aside, what a beast of a receiver.
A Relay for each set of speakers, and a 4th for start-up, 50 amp fuse, Automotive, Goodness gracious. Never ever that big. Always enjoy a switch tear-down and information shared, probably the most problematic thing on Stereo equipment. They have to cut cost to sell for less than the others, criticizing accepted. How in the hell did he get oil on inside of relay ? 288w not bad.
Good job thank man for the show i got a sansui and pioneer i need to have done i guess ill look for a man in the eastern Tennessee area i assume i could do [most] it but if their a fellow with patience like yours for the switches and such ... lol i just say doing the switches for me would be a tall order at least now not happening and lack of experience i would rather not on a 9090db.i got a Realistic monster sized say 30 watt with silly tape deck but silly looks the part i am doing a class amp mod on just because and recap test resistor and replace any know crappy parts i think it will make the unit useful ye know hot rodded a bit may be next week been putting it off way way to long .using WONDOM / Sure Board Power Amp Board TPA3255 x 2 and a 48 volt power supply a good not a china made one 15 amp or so i scored ;] and a sure /i mayy add the wondom DSP board but will add fer sure add A blu tooth 5.0 now it actually does not suck FYI TIP ALL WHO READ THIS .I love all the Wondom /sure boards i bought no fake parts and work well .i suggest the BRU 5mini amp EBAY it rocks and has a usb programable DSP in it software is free on archive org that great cost 45 USD
For a large amp with large caps like that one, the protection circuit usually includes a relay circuit to soften the inrush current as well as speaker switching and protection.
Although that is true I believe the answer to this specific question should rather be: The three relays on the little PCB are speaker selection relays rather than protection relays - you can connect three sets of (stereo) speakers named A, B and C, hence three separate dual pole (--> stereo) relays. Then there is an additional speaker protection relay in series with the three mentioned relays and finally and completely unrelated the bypass relay in the inrush current limiter circuit. Btw.: Some amps combine the selection and protection relays and eliminate the additional main protection relay, cheaper and less resistance in the signal path. (The control circuit might be a bit more complex. Also most amps only have two speaker terminals A and B.)
@@sebastian_harnisch Thank you. I personally have never seen a high end Hitachi stereo receiver. Didn't even know they made them. I believe the 3 speaker outputs do complicate things. Once upon a time I had a receiver, can't remember what brand but it had 3 or 4 speaker set outputs and through relays, when you would command more than 2 sets of speakers it would connect the outputs in series. Below 3 sets parallel. All done with relays.
OMG a Full Recap its like a service for my 1963 EH Holden Australia.
“It’s working fine” famous quote from the owner.
Beautiful receiver, you don't see many of these in the wild anymore. This unit looks to be in great cosmetic condition; your customer will be very happy. Thank you for your time.
Amazing work! Thank you!
I have found that removing the silver oxide (black stuff) from switch contacts does just want you said, you can end up removing all of the silver from polishing. Instead, I put the part in a table salt bath with some aluminum foil. When the silver part touches the foil the oxide almost instantly converts back to silver. This retains the sliver on the part.
Be sure to degrease the part completely. For small parts I spray a couple of oz of Brake Clean into a plastic Rx bottle or Zip-Loc bag along with the part. Shaking it should do the job. If not set the bottle or bag in a water bath in a ultrasonic cleaner. A short ride there will degrease the part. Then give it the short bath in NaCl / H2o with the foil. Great results without sacrificing Q-Tips.
That is a big monster!😮
Thing of beauty. Those capacitors at 9:21 are bigger than transformers in some modern amplifiers or receivers from 2000.
Pretty sure that Dynaharmony refers to the Class G amp circuitry in the BEAST. Love my Hitachi's...two SR-903's, 1 SR-804, and 1 SR-503L. The Monster SR-2004 is quite the find...although the 903's pack more than enough power (75W, with 160W peak power) for my needs. Hitachi's are generally under-rated insofar as brand recognition. It terms of build quality...exceptional. In terms of sound quality...I certainly like Hitachi sound. Note, Hitachi was a key supplier of component parts to all of the major audio equipment brands during the mid to late 70's.
Great work!
I was hoping to see a date code but couldn't, I don't think I've seen that monster before.
I remember the Pioneer receivers from friends houses and a couple of others like Sansui or Toshiba, they were always the owners pride and joy and we were never allowed near them !
Surprised to see plastic insulators behind the transistors, plastic does not conduct heat very well so I wonder how many of those amps had plastic insulators that resulted in the amps being binned ?
1978
Hitachi used that marketing name for its class G amps.
Nice work Trevor, but I wouldn't change active devices that don't match spec or meet minimums. Transistors 2SC1213 Ic=500mA whereas 2sc2240 Ic=100mA. Chasing a problem that wasn't there initially. That aside, what a beast of a receiver.
That BA fuse can be found in the car audio scene. I have gold versions (60A) from the early 2000's.
A Relay for each set of speakers, and a 4th for start-up, 50 amp fuse, Automotive, Goodness gracious. Never ever that big. Always enjoy a switch tear-down and information shared, probably the most problematic thing on Stereo equipment. They have to cut cost to sell for less than the others, criticizing accepted. How in the hell did he get oil on inside of relay ? 288w not bad.
Is it the camera or are the lamps dull. Or my eyes are going bad. Lol. Otherwise nice job sir!
i use switched power to fire a 20 amp contactor to turn on other devices just put a few plugs in a nema box saves the poor switch
That bad boy cost $950 in 1978... $4600 in today's cash. Ouch! You can get a 15 channel at 150 watt each Denon surround receiver for $6500 today.
Did you change all 4 capacitors on power supply
Take pics so you remember
Good job thank man for the show i got a sansui and pioneer i need to have done i guess ill look for a man in the eastern Tennessee area i assume i could do [most] it but if their a fellow with patience like yours for the switches and such ... lol i just say doing the switches for me would be a tall order at least now not happening and lack of experience i would rather not on a 9090db.i got a Realistic monster sized say 30 watt with silly tape deck but silly looks the part i am doing a class amp mod on just because and recap test resistor and replace any know crappy parts i think it will make the unit useful ye know hot rodded a bit may be next week been putting it off way way to long .using WONDOM / Sure Board Power Amp Board TPA3255 x 2 and a 48 volt power supply a good not a china made one 15 amp or so i scored ;] and a sure /i mayy add the wondom DSP board but will add fer sure add A blu tooth 5.0 now it actually does not suck FYI TIP ALL WHO READ THIS .I love all the Wondom /sure boards i bought no fake parts and work well .i suggest the BRU 5mini amp EBAY it rocks and has a usb programable DSP in it software is free on archive org that great cost 45 USD
Noobs and the deoxit bath and 3 in 1 oil smell makes me ill. I have walked away from items reeking of 3in1.
Carver amps had the same thing with the stitching of power DC rails
Why are there three speaker protection relays for 2 channel amp?
For a large amp with large caps like that one, the protection circuit usually includes a relay circuit to soften the inrush current as well as speaker switching and protection.
Although that is true I believe the answer to this specific question should rather be: The three relays on the little PCB are speaker selection relays rather than protection relays - you can connect three sets of (stereo) speakers named A, B and C, hence three separate dual pole (--> stereo) relays. Then there is an additional speaker protection relay in series with the three mentioned relays and finally and completely unrelated the bypass relay in the inrush current limiter circuit.
Btw.: Some amps combine the selection and protection relays and eliminate the additional main protection relay, cheaper and less resistance in the signal path. (The control circuit might be a bit more complex. Also most amps only have two speaker terminals A and B.)
Exactly. Speaker protection circuits are totally separate thing from inrush current limiters@@sebastian_harnisch
@@sebastian_harnisch Thank you. I personally have never seen a high end Hitachi stereo receiver. Didn't even know they made them. I believe the 3 speaker outputs do complicate things. Once upon a time I had a receiver, can't remember what brand but it had 3 or 4 speaker set outputs and through relays, when you would command more than 2 sets of speakers it would connect the outputs in series. Below 3 sets parallel. All done with relays.
TREVOR WHAT HAPPENED TO 9PM MST?
I'm pumping out the vids earlier for our east coast friends
@@TrevorsBench Liking the earlier 5:00pm release time here in SoCal. Thanks Trevor!
Fun seeing a monster receiver on your bench.
VERY IS TOO LONG
Your comment does not make sense😅
@@danielknepper6884 VIDEO IS TOO LONG, IT WAS REPORTED
Nobody forces you to watch.