Hi Everyone,
I'm working on a friend's GFA 5802 and I have a few questions. The first and simplest is does anyone know the real part number for S172 Adcom part # 37005821? I know its made by C&K and that it starts with 7101 but when you plug it into a supplier website it pulls up about 1700 different switches that are made by C&K and that begin with 7101 number. I tried using the model information sheets to figure out which exact part number I want but I couldn't find an exact match to what I measured (I am eyeballing it with a ruler) with multiple close matches on the sheets I'm not sure which ones to go with. So any help there would be appreciated.
When I opened it up I noticed that one of the input boards had either been replaced or repaired since the electrolytic and film caps were different on each input board, as well as the trim pot being different, and the silicone goop on the quick connects isn't present on one of the boards. Are the input boards known to need a recap?
I ask since the channel that has, what looks like the original input board, was less responsive when it came time to adjust the DC offset and I noticed that the DC offset fluctuates in that channel, 6.8 - 8.4 mV approx. it never settles at one value and my friend was having a random hum in that channel on occasion. It had been humming all day and he turned it on to show me, it hummed and then we turned it off and on and then it stopped and wouldn't hum after that, that day. So I'm wondering if it's something on the input board causing it.
When I checked the bias it was running a little low, the lowest output was reading 12 mV across its resistor, I brought up each channel till the lowest was 18 mV and made sure that the highest didn't exceed 33 mV.
So I need to replace the broken switch on the input board (part of the toggle broke off), I'm wondering if I should recap the input board while I have it out?
I'm working on a friend's GFA 5802 and I have a few questions. The first and simplest is does anyone know the real part number for S172 Adcom part # 37005821? I know its made by C&K and that it starts with 7101 but when you plug it into a supplier website it pulls up about 1700 different switches that are made by C&K and that begin with 7101 number. I tried using the model information sheets to figure out which exact part number I want but I couldn't find an exact match to what I measured (I am eyeballing it with a ruler) with multiple close matches on the sheets I'm not sure which ones to go with. So any help there would be appreciated.
When I opened it up I noticed that one of the input boards had either been replaced or repaired since the electrolytic and film caps were different on each input board, as well as the trim pot being different, and the silicone goop on the quick connects isn't present on one of the boards. Are the input boards known to need a recap?
I ask since the channel that has, what looks like the original input board, was less responsive when it came time to adjust the DC offset and I noticed that the DC offset fluctuates in that channel, 6.8 - 8.4 mV approx. it never settles at one value and my friend was having a random hum in that channel on occasion. It had been humming all day and he turned it on to show me, it hummed and then we turned it off and on and then it stopped and wouldn't hum after that, that day. So I'm wondering if it's something on the input board causing it.
When I checked the bias it was running a little low, the lowest output was reading 12 mV across its resistor, I brought up each channel till the lowest was 18 mV and made sure that the highest didn't exceed 33 mV.
So I need to replace the broken switch on the input board (part of the toggle broke off), I'm wondering if I should recap the input board while I have it out?
There are lots of variations on parts like that switch, it could be mechanical, electrical, even color,
type of actuator lever, etc. Also, try using a micrometer.
GFA-5802 issues. Oh Jeez, where to begin!? I stopped servicing this model for lots of reasons.
Not sure what to tell you about the switch. That's one part I never had trouble with on a 5802! Maybe you can find a nice, round, industrial panel switch?
- Heat - Not enough heatsink for that much bias. (540VA idle) The sinks run at about 125-130F on the outside. It's an oven inside.
- Burned-up, leaky input mosfets. These puppies run way too hot! It also scorches the circuit board and lifts traces. Fix: Attach small heatsinks with thermal epoxy. First, hone the surfaces flat with a diamond file.
- Fragile circuit boards. - The traces lift easily. Use a good regulated iron and and a lower temperature than usual.
- Quality control. - I've seen metal debris stuck under the output TO-3's on at least three different GFA-5802's. This issue had me chasing my tail for a while.
And I've seen several 5802s with this bodgey arrangement. The power supply board sits on top of the PS capacitors, along with these terminals that connect to the binding posts. So when the factory couldn't get the exact same height capacitors anymore, they resorted to bending the bracket and terminals. Ew.
- Burned-up power supply capacitor pads.
The amp consumes 540VA at idle, so I assume these pads are heating up and corroding away, and they will start sparking eventually. This is made worse by the star-washers chewing up the trace. They should have put some via stitching around the holes. My fix is to solder a gold-plated washer over the hole, like so...
- Marshmallow-sized caps C40 and C58 are usually fried from the heat and stress. These are 4700/16V caps. I replace with 5600/25V 105C.
- Leaky zener protection diodes. Maybe they get leaky from doing their job and shunting a static shock, but I suggest replacing all the zener protection diodes. Sometimes one of the zeners in the string that regulates the high-voltage supply will go bad. Leaky zeners sometimes cause a lack of bias.
- 555 Timers often burn out. I replace with SE-555, not sure if the mil-spec really helps, but none of my customers have had issues.
- Heatsinks not grounding! The whole chassis is powder-coated, and so sometimes no metal-on metal connection is made to the heatsink because the screws don't cut through. Scrape away the paint around the screw hole; one for each half of the heatsink. Use a star-washer. Do the front panel and top cover too.
Not sure what to tell you about the switch. That's one part I never had trouble with on a 5802! Maybe you can find a nice, round, industrial panel switch?
Need help w/ biasing
1) When you turn on amp the left channel is @ zero bias
2) I turned the potentiometer to set bias to 33 mv across the bias resistor, and it stays there until I turn it on again
3) After I turned off and have it cooled, and turn on again the bias is @ zero again
4) I replaced the electrolytic caps, and the 555 timer
5) Still same problem
1) When you turn on amp the left channel is @ zero bias
2) I turned the potentiometer to set bias to 33 mv across the bias resistor, and it stays there until I turn it on again
3) After I turned off and have it cooled, and turn on again the bias is @ zero again
4) I replaced the electrolytic caps, and the 555 timer
5) Still same problem
Hey Rexcamacho,
I suspect the protection zeners, D69, D70, D94, D28, or the IRF9610 input mosfets, as described above. Check the source of the input mosfets and you should see around 4V.
A quick way to check for this, is to install your working input board from the right channel. (though it does not rule out the protection zeners D28 and D94 on the output boards.)
If you need to replace the mosfets, you'll need to buy a bunch and match them for Vgs, as Nelson desribes here...
PassDiy
I suspect the protection zeners, D69, D70, D94, D28, or the IRF9610 input mosfets, as described above. Check the source of the input mosfets and you should see around 4V.
A quick way to check for this, is to install your working input board from the right channel. (though it does not rule out the protection zeners D28 and D94 on the output boards.)
If you need to replace the mosfets, you'll need to buy a bunch and match them for Vgs, as Nelson desribes here...
PassDiy
For what it's worth, below is a list of all the caps, zeners, relay, 555timer and switch I ordered from Mouser. I'm doing an overhaul on one and I saw this so I thought i'd share for future schadenfreude 5802 ists. Total cost= $240
Thank you Phloodpants for all the info here and on your website! I couldn't have done it without you.
The switch the switch, of picking out all of this stuff C&Ks part ordering system was the most difficult. The part I ordered (I think) has 3 straight pins that I will bend into place. It was the only way I could be sure it would work.
Mouser:
Mfr.:
ON Semiconductor
Mfr.'s Part #:
1N4148
Desc.:
Diodes - General Purpose, Power, Switching 100V Io/200mA BULK
1
1 Ships Now
$0.10
$0.10
Mfr.:
Omron
Mfr.'s Part #:
G5LE-1A-E-DC12
Desc.:
General Purpose Relays Power PCB Relay SPST-NO 12VDC
1
1 Ships Now
$2.15
$2.15
Mfr.:
United Chemi-Con (UCC)
Mfr.'s Part #:
E32D101HPN223MDA5M
Desc.:
Aluminum Electrolytic Capacitors - Screw Terminal 22000uF 100 Vol ...
4
4 Ships Now
$25.72
$102.88
Mfr.:
Nichicon
Mfr.'s Part #:
UHW1E562MHD
Desc.:
Aluminum Electrolytic Capacitors - Radial Leaded 5600uF 25 Volts ...
2
2 Ships Now
$3.01
$6.02
Mfr.:
WIMA
Mfr.'s Part #:
MKS4J021002B00KSSD
Desc.:
Film Capacitors 630V .01uF 10%
1
1 Ships Now
$0.34
$0.34
Mfr.:
Vishay
Mfr.'s Part #:
IRFD210PBF
Desc.:
MOSFET N-CH 200V HEXFET MOSFET HEXDI
48
48 Ships Now
$0.758
$36.38
Mfr.:
Microchip
Mfr.'s Part #:
1N759A
Desc.:
Zener Diodes Zener Diodes
18
18 Ships Now
$2.34
$42.12
Mfr.:
Microchip
Mfr.'s Part #:
1N4754AGe3
Desc.:
Zener Diodes Zener Diodes
6
6 Ships Now
$4.93
$29.58
Mfr.:
WIMA
Mfr.'s Part #:
MKS4F032203F00JI00
Desc.:
Film Capacitors .22uF 250 Volts 5%
4
4 Ships Now
$0.70
$2.80
Mfr.:
WIMA
Mfr.'s Part #:
MKP2G011001B00JSSD
Desc.:
Film Capacitors 400V 1000pF 5%
2
2 Ships Now
$0.50
$1.00
Mfr.:
WIMA
Mfr.'s Part #:
FKP3G003302B00MSSD
Desc.:
Film Capacitors 330pF 20% 400V 3x8.5x10
4
4 Ships Now
$0.42
$1.68
Mfr.:
C&K Switches
Mfr.'s Part #:
7101SDW5GE
Desc.:
Toggle Switches SPDT ON-ON
1
1 Ships Now
$8.16
$8.16
Mfr.:
Texas Instruments
Mfr.'s Part #:
SE555P
Desc.:
Timers & Support Products Precision
2
2 Ships Now
$0.43
$0.86
Mfr.:
WIMA
Mfr.'s Part #:
MKS4F031002C00JSSD
Desc.:
Film Capacitors 250V .1uF 5% LS 7.5mm
6
6 Ships Now
$0.46
$2.76
Mfr.:
Nichicon
Mfr.'s Part #:
UHE1H100MDD1TD
Desc.:
Aluminum Electrolytic Capacitors - Radial Leaded 10uF 50V 20% Min ...
4
4 Ships Now
$0.29
$1.16
Mfr.:
Panasonic
Mfr.'s Part #:
EEU-EB1E101SB
Desc.:
Aluminum Electrolytic Capacitors - Radial Leaded 100uF 25volts AE ...
2
2 Ships Now
$0.34
$0.68
Mfr.:
Panasonic
Mfr.'s Part #:
EEU-EE2E101
Desc.:
Aluminum Electrolytic Capacitors - Radial Leaded 100uF 250volts A ...
2
2 Ships Now
$1.77
$3.54
Mfr.:
Aavid
Mfr.'s Part #:
501100B00000G
Desc.:
Heat Sinks Extruded Style Heatsink with Epoxy Attach-On for DIPS, ...
4
4 Ships Now
$0.58
$2.32
Mfr.:
Nichicon
Mfr.'s Part #:
UFG1J470MPM
Desc.:
Aluminum Electrolytic Capacitors - Radial Leaded 47uF 63 Volts 20 ...
4
4 Ships Now
$0.63
$2.52
Thank you Phloodpants for all the info here and on your website! I couldn't have done it without you.
The switch the switch, of picking out all of this stuff C&Ks part ordering system was the most difficult. The part I ordered (I think) has 3 straight pins that I will bend into place. It was the only way I could be sure it would work.
Mouser:
Mfr.:
ON Semiconductor
Mfr.'s Part #:
1N4148
Desc.:
Diodes - General Purpose, Power, Switching 100V Io/200mA BULK
1
1 Ships Now
$0.10
$0.10
Mfr.:
Omron
Mfr.'s Part #:
G5LE-1A-E-DC12
Desc.:
General Purpose Relays Power PCB Relay SPST-NO 12VDC
1
1 Ships Now
$2.15
$2.15
Mfr.:
United Chemi-Con (UCC)
Mfr.'s Part #:
E32D101HPN223MDA5M
Desc.:
Aluminum Electrolytic Capacitors - Screw Terminal 22000uF 100 Vol ...
4
4 Ships Now
$25.72
$102.88
Mfr.:
Nichicon
Mfr.'s Part #:
UHW1E562MHD
Desc.:
Aluminum Electrolytic Capacitors - Radial Leaded 5600uF 25 Volts ...
2
2 Ships Now
$3.01
$6.02
Mfr.:
WIMA
Mfr.'s Part #:
MKS4J021002B00KSSD
Desc.:
Film Capacitors 630V .01uF 10%
1
1 Ships Now
$0.34
$0.34
Mfr.:
Vishay
Mfr.'s Part #:
IRFD210PBF
Desc.:
MOSFET N-CH 200V HEXFET MOSFET HEXDI
48
48 Ships Now
$0.758
$36.38
Mfr.:
Microchip
Mfr.'s Part #:
1N759A
Desc.:
Zener Diodes Zener Diodes
18
18 Ships Now
$2.34
$42.12
Mfr.:
Microchip
Mfr.'s Part #:
1N4754AGe3
Desc.:
Zener Diodes Zener Diodes
6
6 Ships Now
$4.93
$29.58
Mfr.:
WIMA
Mfr.'s Part #:
MKS4F032203F00JI00
Desc.:
Film Capacitors .22uF 250 Volts 5%
4
4 Ships Now
$0.70
$2.80
Mfr.:
WIMA
Mfr.'s Part #:
MKP2G011001B00JSSD
Desc.:
Film Capacitors 400V 1000pF 5%
2
2 Ships Now
$0.50
$1.00
Mfr.:
WIMA
Mfr.'s Part #:
FKP3G003302B00MSSD
Desc.:
Film Capacitors 330pF 20% 400V 3x8.5x10
4
4 Ships Now
$0.42
$1.68
Mfr.:
C&K Switches
Mfr.'s Part #:
7101SDW5GE
Desc.:
Toggle Switches SPDT ON-ON
1
1 Ships Now
$8.16
$8.16
Mfr.:
Texas Instruments
Mfr.'s Part #:
SE555P
Desc.:
Timers & Support Products Precision
2
2 Ships Now
$0.43
$0.86
Mfr.:
WIMA
Mfr.'s Part #:
MKS4F031002C00JSSD
Desc.:
Film Capacitors 250V .1uF 5% LS 7.5mm
6
6 Ships Now
$0.46
$2.76
Mfr.:
Nichicon
Mfr.'s Part #:
UHE1H100MDD1TD
Desc.:
Aluminum Electrolytic Capacitors - Radial Leaded 10uF 50V 20% Min ...
4
4 Ships Now
$0.29
$1.16
Mfr.:
Panasonic
Mfr.'s Part #:
EEU-EB1E101SB
Desc.:
Aluminum Electrolytic Capacitors - Radial Leaded 100uF 25volts AE ...
2
2 Ships Now
$0.34
$0.68
Mfr.:
Panasonic
Mfr.'s Part #:
EEU-EE2E101
Desc.:
Aluminum Electrolytic Capacitors - Radial Leaded 100uF 250volts A ...
2
2 Ships Now
$1.77
$3.54
Mfr.:
Aavid
Mfr.'s Part #:
501100B00000G
Desc.:
Heat Sinks Extruded Style Heatsink with Epoxy Attach-On for DIPS, ...
4
4 Ships Now
$0.58
$2.32
Mfr.:
Nichicon
Mfr.'s Part #:
UFG1J470MPM
Desc.:
Aluminum Electrolytic Capacitors - Radial Leaded 47uF 63 Volts 20 ...
4
4 Ships Now
$0.63
$2.52