2275 rebuild project
- Thread starter thxdave
- Start date
Steven Tate
CEO Flat Forehead Soc.
Great looking work! You're going to have an awesome sounding receiver set to go for another 30 years. 
I was able to bring the soldering gun tip close enough to the shrink to make it snug up nicely. I figured this would be kinder to the surrounding parts instead of hitting it with my heat guy. BTW, what is the purpose of bundling those two transistors together like this?
I use the soldering iron tip too for the same reason. They are held together to keep them at the same temperature. Transistor gain varies with heat so this way the gain on each stays close and therefore the bias stays more stable and probably the dc offset but don't quote me on that!
There's no biasing involved in the usage I am referring to in the power supply, it's just a pass transistor.
Hello, As far I know the 2SC458 are pure evil, must go... watch out for the pinout.
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Yes (agreeing with Hipocrates!), but again this has nothing to do with what I was suggesting just to be clear.
@BabyChicken ... I think so; but you should create your own thread, Is not ok to piggy back on someone else thread because, it can become a mess.
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I'll have to verify when I get back home tonight but the parts list is higher up in the thread and you can look at it on Mouser. I'm getting ready to do the Phono board or the Tone board next. I've delayed it because I'm having so much fun listening to the 2275 as I progress through it!
Leestereo
Super Member
C702 is the DC blocking capacitor for the negative feedback loop, i.e., it's in the signal path and hence is best served by a bipolar type.
Working on the phono board this weekend so more pix coming. I also wanted to extend the offer I made to Steven re: the insulating fiberglass material. If anybody would like to try a chunk, just PM me and I'll mail you a length of it (approx. 24"). I have WAY more of it than I"ll need in one lifetime!
Steven Tate
CEO Flat Forehead Soc.
I have already used this fiberglass sleeve on the hottest resistor in my 2325. Not a lot of listening time so far, so time will tell how it holds up in a high heat situation. Thanks, Dave!
I came very close to screwing up tonight with C413 on the P400 board. Following Leestereo's specs, I'm substituting the axial 100uF/35v cap with a radial 270uF/50v by utilizing the closely spaced, predrilled holes (thank you Marantz!) that were unused. I made a mistake by not reading the schematic nor confirming where the circuit board trace went. I blindly followed the "+" sign nearest the hole seen here:
Luckily, Ben caught my mistake before I got too far along. I flipped the cap around, resoldered and now I'm cursing getting these damned transistors desoldered! ;-) How many of you use braid and how many use desoldering guns....and I don't mean those bulb-types but actual vacuum guns?
This near screw-up taught me a valuable lesson about verifying parts orientation even when you think you know how the part should be installed.
Luckily, Ben caught my mistake before I got too far along. I flipped the cap around, resoldered and now I'm cursing getting these damned transistors desoldered! ;-) How many of you use braid and how many use desoldering guns....and I don't mean those bulb-types but actual vacuum guns?
This near screw-up taught me a valuable lesson about verifying parts orientation even when you think you know how the part should be installed.
Steven Tate
CEO Flat Forehead Soc.
What?? I was working on what looks like the identical board in my 2325 yesterday. I removed the axial cap and had ordered a PW series 270uF/50V radial cap to replace it (axial replacement was $47!). When I installed it, I just felt like it was too tall and might short with the bottom of the case, so I took it off and replaced the axial cap for now. But the axial definitely had negative on the left in your pic. I can see now that the traces cause the negative to be on your right in your pic and the + sign is incorrect. I was definitely going to do it wrong. I'm glad I didn't like the height of that cap or I would have already fired it up and had a major problem.
Steve
Steve
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Leestereo
Super Member
The PW 270µF/50V that Mouser stocks is definitely too tall as a replacement for C413; however, this UCC
270µF/50V (EKY-500ETD271MJ16S) measures only 10mm x 16mm:
(http://www.mouser.com/ProductDetail...=sGAEpiMZZMtZ1n0r9vR22RoXgSGI60nWl6UkFipQzFE=)
Steven Tate
CEO Flat Forehead Soc.
Thanks! I will definitely be getting one of those. I can't believe how lucky I was that the cap was so tall. Otherwise, I would have fired that baby up with it in backward - along with the unpleasant surprises that brings.
Actually the "+" sign is correct, it's just for the axial cap. The long silkscreened lines indicate the holes for the axial part. It sure would have been NICE if they would have mad the pads and drill hits so that either orientation of cap could use the "+" sign correctly. #*&)(_)(*&%#$!
Steven Tate
CEO Flat Forehead Soc.
I agree completely!