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65.32.44.15
In the owner's manual it states "a provision has been made on the pcb...(in the form of two unused "eyelets") to allow easy modification" of the impedance of the phono input to vary from 47k/100pF. Does anyone know which eyelets these are? There's a 10 ohm resistor in R101, (I think) is that it? I think this would give me a circa 9k ohm load if that's the case. I'm interested in changing loading, can anyone point me to a tutorial? I've seen the Hagerman loading page and a few random posts on various BBs. Any and all help greatly appreciated.
Peas
Follow Ups:
A service manual for this unit can be purchased from http://www.vintageaudiomanuals.com/They also sell through e-bay, which I've found to be an easier way to go.
As I replied to your duplicate posting in Tubes DIY, two resistors in parallel will ALWAYS be less total composite value than the lowest of the two. The formula for two R in parallel is: RT=(R1XR2)/(R1+R2). So, 47,000 X 10 = 470,000 and 47,000 + 10 = 47,010 and 470,000/47,010 = 9.99 ohms, NOT 9,000 ohms as you mis-calculated. IOW this is not it.
because I'm also seeking information about the circuit board in the GFP. I do appreciate your response. What does IOW stand for?
I just was not certain if you went back to view any replys. IOW is keyboard slang for In Other Words (you may Google search for a complete keyboard slang dictionary). As a registered inmate, you can pull up any of your own posts & scroll to very bottom for a Delete function (which must be implemented within 24 hours & prior to any replys) & thereby self-edit or remove.
never heard that one, though. I wasn't aware of the delete function, good info. Thanks!
Have you tried contacting Adcom support??That's where I'd start
I'd be curious as to their level of customer service
Julien
"There's someone in my head, but it's not me"
I don't know how willing they would be to provide service information to a non-dealer or service center. I'll shoot them an email just the same.
Good luck with Adcom's service dept. I hope the customer service is better than the service a repair shop can get.I've recently worked on a GFP-555, not a 555II, BUT:
In the GFP-555, the phono stage is on the side opposite the power supply (for obvious reasons), and consists of 2 opamps right next to each other, with their respective supporting components. I'm not sure if the 555II is all discrete or not, but most likely not. Anyway, in between those opamps and the phono input jacks is where the spot to plug in resistors/caps should be. They may look more like little tubes than eyelets. It's been awhile since I've seen inside, cannot remember the exact location, but definitely between the input jacks and the opamps.
BT
Found it! The resistors are in R103 and R104, there are parallel eyelets in the PCB adjacent to each resistor. The caps are in C101 and C102. I can add resistance in parallel easily. I'll have to either replace the caps with different values or solder them in elsewhere.
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