Rotel RB-850
25W light bulb
(1) Turn on = very bright
(2) Steady on = above glow. . .verge of being bright
DC offset 2x to 3x in the 60mV range
70W light bulb (583mA at 260ohms hot, 14ohms cold)
(1) Turn On = very bright for 2 seconds
(2) Steady Running = low glow (less than M-45)
DC offset elevated about 1.8x
Amplifier on and running at
6.6V/8ohms = 5.4W x 2 channels
Light bulb bright but not fully bright. . .
25W light bulb
(1) Turn on = very bright
(2) Steady on = above glow. . .verge of being bright
DC offset 2x to 3x in the 60mV range
70W light bulb (583mA at 260ohms hot, 14ohms cold)
(1) Turn On = very bright for 2 seconds
(2) Steady Running = low glow (less than M-45)
DC offset elevated about 1.8x
Amplifier on and running at
6.6V/8ohms = 5.4W x 2 channels
Light bulb bright but not fully bright. . .
Replacement Power Transistors for Yamaha M-45
Original:
A1265n [Toshiba 2SA1265n] pnp
C3182n [Toshiba 2SC3182n] npn
Replacements:
2SA1941 pnp
or nte37(mouser) cross ref to Sanyo 2SB817 [used in RB850]
2SC5198 npn
or nte36(mouser) cross ref to Sanyo 2SD1047 [used in RB850]
Mouser has the pair 526-NTE37-MCP for $10.13!
Original:
A1265n [Toshiba 2SA1265n] pnp
C3182n [Toshiba 2SC3182n] npn
Replacements:
2SA1941 pnp
or nte37(mouser) cross ref to Sanyo 2SB817 [used in RB850]
2SC5198 npn
or nte36(mouser) cross ref to Sanyo 2SD1047 [used in RB850]
Mouser has the pair 526-NTE37-MCP for $10.13!
Here is a web site with a good selection of replacement transistors.
http://audiolabga.com/
might have to buy a bunch to get them to be matched.
That is good advice. NTE bad for audio (mostly at mouser).
http://audiolabga.com/
might have to buy a bunch to get them to be matched.
That is good advice. NTE bad for audio (mostly at mouser).
Continuing work on blow output transistors:
Traced more problems back to the driver board.
5 total transistors
2SA1306 (clamped to heatsink)
2SC3298 (clamped to heatsink)
A970
C2240 (back blown off)
'unknown' (clamped to heatsink)
3 resistors
(1) 100ohm (fried chicken) on emitter of 2SC3298
(2) 1.1kohm
2 caps
A220J Soshin
I'm wondering out loud if I should just replace all parts?
I'm seriously thinking of pulling the same channel from the
other M-45 and dropping it in. . .
Traced more problems back to the driver board.
5 total transistors
2SA1306 (clamped to heatsink)
2SC3298 (clamped to heatsink)
A970
C2240 (back blown off)
'unknown' (clamped to heatsink)
3 resistors
(1) 100ohm (fried chicken) on emitter of 2SC3298
(2) 1.1kohm
2 caps
A220J Soshin
I'm wondering out loud if I should just replace all parts?
I'm seriously thinking of pulling the same channel from the
other M-45 and dropping it in. . .
Attachments
Maybe I'm slow. . . .but is the consensus that AudioLabs in GA is
supplying knockoff transistors? NTE seems to have some bad rap.
I started a thread in parts to compile a list of parts suppliers.
I want to keep it simple. . .
Example:
Company A Name: good caps, expensive shipping
Company B Name: quality transistors, limited stock
Company C Name: knowledgeable sales staff, good return policy
etc.
supplying knockoff transistors? NTE seems to have some bad rap.
I started a thread in parts to compile a list of parts suppliers.
I want to keep it simple. . .
Example:
Company A Name: good caps, expensive shipping
Company B Name: quality transistors, limited stock
Company C Name: knowledgeable sales staff, good return policy
etc.
After much time researching the replacement
transistors I've come to a cross-roads.
Option A:
Continue to hunt for quality transistors for +20 year old amplfier.
Plus: Restore original amplifer sound at reasonable cost (<$50)
Minus: Might not work, more time hunting down other problems,
replacement transistors might not be matched and/or fakes.
Option B:
Swap out amplifier section and replace with new amp modules.
Plus: Quality amplifier modules, new technology, more support.
Minus: Mod power supply to work with module, different sound quality.
In the end. . .I like having three quality working amplfiers. I would also
like to keep the power meters functioning. I will be doing some
non-distructive testing of the meters to see if it will work.
Why I'm leaning towards the ColdAmp modules.
They accept the +/- 63VDC power rails of the M-45.
They run cooler than most Class AB amps and would mount
easily on the existing heatsinks.
They are relatively cheap at $300 US dollar for two modules plus
shipping. I originally paid about $410 for the M-45.
Good opportunity to reuse existing parts (instead of landfill).
transistors I've come to a cross-roads.
Option A:
Continue to hunt for quality transistors for +20 year old amplfier.
Plus: Restore original amplifer sound at reasonable cost (<$50)
Minus: Might not work, more time hunting down other problems,
replacement transistors might not be matched and/or fakes.
Option B:
Swap out amplifier section and replace with new amp modules.
Plus: Quality amplifier modules, new technology, more support.
Minus: Mod power supply to work with module, different sound quality.
In the end. . .I like having three quality working amplfiers. I would also
like to keep the power meters functioning. I will be doing some
non-distructive testing of the meters to see if it will work.
Why I'm leaning towards the ColdAmp modules.
They accept the +/- 63VDC power rails of the M-45.
They run cooler than most Class AB amps and would mount
easily on the existing heatsinks.
They are relatively cheap at $300 US dollar for two modules plus
shipping. I originally paid about $410 for the M-45.
Good opportunity to reuse existing parts (instead of landfill).
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