Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Please login or register.

Login with username, password and session length
Advanced search  

News:

SSGuitar has moved to PHP 7.1, enjoy the speed!

collapse
Pages: 1 2 [3] 4   Go Down

Author Topic: National GA920P Schematic  (Read 9521 times)

clintrubber

  • SSGuitar Regular
  • ***
  • Chip Points: 0
  • Posts: 11
    • View Profile
Re: National GA920P Schematic
« Reply #30 on: November 02, 2017, 12:44:22 PM »

Aha, that auction just finished, 8 bids, winning bid US $57,66

Perhaps better not using mine as a donor-chassis/enclosure ;-)

Logged

galaxiex

  • Legendary
  • ******
  • Chip Points: 41
  • Posts: 486
    • View Profile
Re: National GA920P Schematic
« Reply #31 on: November 02, 2017, 07:34:00 PM »

Ahh yes... I was also watching that listing.
Just curious to see what it sold for.

I already have two so I don't need another one.  ;)
Logged
Fear leads to Anger, Anger leads to Hate, Hate leads to Suffering.

clintrubber

  • SSGuitar Regular
  • ***
  • Chip Points: 0
  • Posts: 11
    • View Profile
Re: National GA920P Schematic
« Reply #32 on: November 05, 2017, 07:05:30 PM »

Just curious to see what it sold for.

Same here, it didn't do too bad I guess.

OK, FWIW, a few quick and low-qual pics for now, this is mine with the 'blue left front', and the reverb tank right behind the front panel.

Bye


Logged

galaxiex

  • Legendary
  • ******
  • Chip Points: 41
  • Posts: 486
    • View Profile
Re: National GA920P Schematic
« Reply #33 on: November 05, 2017, 07:30:42 PM »

Thanks for the pics.  :)

Interesting layout compared to the others.

Can you do a overall shot that shows the whole chassis.
Thanks!
Logged
Fear leads to Anger, Anger leads to Hate, Hate leads to Suffering.

clintrubber

  • SSGuitar Regular
  • ***
  • Chip Points: 0
  • Posts: 11
    • View Profile
Re: National GA920P Schematic
« Reply #34 on: November 10, 2017, 08:25:48 AM »

Interesting layout compared to the others.

All those iterations are a bit puzzling/amusing! :-)  ... why ?!  8)

Quote
Can you do a overall shot that shows the whole chassis.

Here we go, 3 more pics, have a good weekend!
Logged

clintrubber

  • SSGuitar Regular
  • ***
  • Chip Points: 0
  • Posts: 11
    • View Profile
Re: National GA920P Schematic
« Reply #35 on: November 10, 2017, 08:29:27 AM »

BTW, imho 5 Fender knobs look way better on this little amp than the bit smallish originals... just personal preference
Logged

galaxiex

  • Legendary
  • ******
  • Chip Points: 41
  • Posts: 486
    • View Profile
Re: National GA920P Schematic
« Reply #36 on: November 10, 2017, 10:36:24 PM »

Thanks for the pics!   :tu:

Looks like the reverb tank is "upside down" compared to both of the other ones.

I agree, all those iterations are a bit puzzling/amusing! 

Why? Who knows.   8) Different factory, different production run etc.

I too like the look of Fender knobs, but on these amps my personal preference is for the original knobs.
To each his own.  :)

Thanks again for sharing!  :tu:
Logged
Fear leads to Anger, Anger leads to Hate, Hate leads to Suffering.

lotus1

  • SSGuitar Apprentice
  • **
  • Chip Points: 0
  • Posts: 9
    • View Profile
Re: National GA920P Schematic
« Reply #37 on: December 16, 2017, 09:37:15 AM »

Hello, I just discovered this forum and thread. Very cool. Have a question tho. I have a national GA 960P amplifier.I am in need of a schematic or someone who has one as I have 2 resistors that need replacing but, have burned up to the point I can't read values. If anyone has one of this model, would very much appreciate any help. It uses 2SD428 output transistors. Thanks all.Mario
Logged

Jazz P Bass

  • Master SSGuitarist
  • ****
  • Chip Points: 9
  • Posts: 78
    • View Profile
Re: National GA920P Schematic
« Reply #38 on: December 16, 2017, 02:31:02 PM »

It may help if you describe where the resistors go.

What points do they attach to?
Resistors burn up when another part of the circuit demands eccess current.
« Last Edit: December 16, 2017, 05:11:44 PM by Jazz P Bass »
Logged

DrGonz78

  • Legendary
  • ******
  • Chip Points: 66
  • Posts: 529
    • View Profile
Logged
“A person who never made a mistake never tried anything new.” -Albert Einstein

Jazz P Bass

  • Master SSGuitarist
  • ****
  • Chip Points: 9
  • Posts: 78
    • View Profile
Re: National GA920P Schematic
« Reply #40 on: December 16, 2017, 05:12:13 PM »

Wow!

Those two schematics are totally different.

As the OP is searching for a schematic that uses 2SD428 (TO3 mount) the schematics may or may not be of help.

Maybe the Gibson G30 is closer.
« Last Edit: December 16, 2017, 05:44:41 PM by Jazz P Bass »
Logged

lotus1

  • SSGuitar Apprentice
  • **
  • Chip Points: 0
  • Posts: 9
    • View Profile
Re: National GA920P Schematic
« Reply #41 on: December 16, 2017, 08:39:02 PM »

It may help if you describe where the resistors go.

What points do they attach to?
Resistors burn up when another part of the circuit demands eccess current.
Yes, I understand, Was looking for the schematic but, Here's a couple of pics. It's the red ones connected to the transistor itself. One has the red wird connected directly, not sure why that is. Thanks for the replies, really like this amp, would like to get it running again. Mario
Logged

phatt

  • Legendary
  • ******
  • Chip Points: 216
  • Posts: 1844
    • View Profile
Re: National GA920P Schematic
« Reply #42 on: December 16, 2017, 09:01:56 PM »

Those resistors will most likely be half an Ohm. (OR47)
Most likely reason for them burning up is someone plugging in an extra speaker which puts more current demand on the circuit.
These type of power circuits are basic in design and don't handle low Z speaker loads well.
re the red wire Q.   A; who ever fixed it last was lazy. :trouble

Replace those resistors and use the light bulb limiter (Instructions at top of this forum)

Phil.
Logged

lotus1

  • SSGuitar Apprentice
  • **
  • Chip Points: 0
  • Posts: 9
    • View Profile
Re: National GA920P Schematic
« Reply #43 on: December 16, 2017, 10:09:19 PM »

1/2? Thanks.  Was told the transistors went bad, they were replaced but, resistors, no.and yes, he was lazy... Haven't gone in myself as without a schematic, I don't touch...or help. I will rectify both the resistors and shoddy wiring, will report back. Oh, and the amp was only used with the cabinet it came with, a 2x12...haven't measured cabinet Z yet, so...It does look like the original cabinet. Will post more pics in the morning,Thanks.<
Logged

lotus1

  • SSGuitar Apprentice
  • **
  • Chip Points: 0
  • Posts: 9
    • View Profile
Re: National GA920P Schematic
« Reply #44 on: December 17, 2017, 07:44:43 AM »

More Pics.
Logged
Pages: 1 2 [3] 4   Go Up
 

* User Controls
 
 
Welcome, Guest. Please login or register.
Did you miss your activation email?
* Recent Posts
Thinking about building a SS amp by phatt
[Today at 10:02:25 AM]


How to build an amp to run on solar power by Bill Moore
[June 20, 2018, 06:28:51 PM]


Marshall 8080 combo blowing fuse and more by J M Fahey
[June 19, 2018, 11:59:32 AM]


Need some ideas for a new head purchase - SS/Hybrid/Valve by J M Fahey
[June 19, 2018, 11:39:03 AM]


Hohner Pianet Amplifier Low Output by J M Fahey
[June 17, 2018, 05:15:51 PM]

* Sponsors