Fisher RS1080 Fishing4 Preamp Crackle source!

Iusnas-0009G

New Member
I am open to some help here. First of all this Receiver is the BOMB! It is contending for first place in my stable, even while having trouble in its preamp! I will post picks when it is in one piece so all can see!
All Controls/Volume have been treated with a healthy treatment of Deoxit! Preamp has been singled out ! Both CH's have distortion and crackle one CH with lower volume and consistent noise, and the other intermittent but much louder when it hits!(like thunder w/ crackle) I have been searching AK and found the same symptoms in other Receivers ! But rarely a follow up!
Coupling cap seems to be the logical culprit or perhaps a transistor in the signal path? I have been checking and cleaning for many hours,making good progress! I found a few trouble spots and repaired them . Now It is a faulty component I seek.
I have been building a bench and I am very comfortable with a soldering iron. Seems tracing the signal path with a scope is the right course? Can you measure ESR on a cap under 1uf ? Meter states 1uf- 22000uf as test range. I think they are referring to capacitance not ESR value? If not what happens most often to the small coupling caps ? Short or partial short? Any Multimeter /tricks for Testing ? Any trouble shooting ideas would be greatly appreciated! I am waiting for a copy of SM. Thank you all!
 
The symptoms you described could still be caused by dirty switches, not pots. Clean the TONE DEFEAT, LOUDNESS, TAPE MONITOR, MUTING and any FILTER switches.

You would be surprised at how those switches, when not cleaned properly of the pitted carbon, can affect the sound!

First eliminate all switches as suspects!
 
Same receiver I am working on right now. I had static and 1 CH cutting out but this was really only when you would turn the volume control unless you left it on a bad spot. I ended up taking out the board and then removing the control and taking it apart and cleaning it all up etc back together and what a difference - like night and day. Worth the hassel of getting that darn clip thing off the back that holds it all together.
 
This is the largest and heaviest receiver I've got, and the newest... could dethrone my 16.5 as :king: king receiver, we'll see...

I really enjoyed reading everything yrly, Sanyofreak, CULater, Fisherdude and others wrote about it on AK. :thmbsp::D:thmbsp::D:thmbsp:

cademan is right about those infrequently used switches often contributing to problems. hamrules is right that it's worth it to go all out on those controls. Open up, spray, clean, flush, spray again.

On mine some bonehead :headscrat: bypassed the balance control, which is probably broken. I'm happy to have a working 1080 though. :D:music: The control is just a little annoying, since some of my listening rooms aren't perfectly symmetrical :no:

Unlikely to get an exact replacement control so I'll try to fit an equivalent in there once I figure out the value. Til then a preamp could make do; seems a little overkill to use my C-4 as a balance knob... :dunno:

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That balance control had a number on it of 9-25590 with a value of 250KohmX2 soldered on the board (6 pins) type.
 
Cleaning

Yes hamrules I noticed quite the improvement after cleaning the volume control on the Rs1080! But it didn't repair/replace the fault as cause of my heavy distortion. I am waiting for a copy of the SM . I am finding coupling caps with 4 # codes printed on them for ID and value. Gray Sanyo caps. I believe these to be my source of noise.
How long have you had your RS1080? Is the Volume the main focus with your Receiver? The Rs1080 is one Super impressive Receiver! I am blessed with mine!
And looking forward to returning this one to good health.
 
Had it now for a couple of months only. Can't believe how darn loud this thing can go without the least effort at all. I got a bit carried away with it replacing parts just becuase. Even swapped out every single screw and replaced with stainless steel - can't control myself. Couple of small transistors and that odd dual tapped cap with 2 seprate ones built into 1 - parts will be here in a couple days. Then just the indicator lights to mount in a new housing and hopefully all will be good. If not the only issue will be the turn on thump from the protector relay - it's much better but sill there. When you get the manual be careful of some stuff in it as there are errors. It seems the point to point wiring part has mistakes versus the schematic and the point to point is wrong.
 
Only 2 of my amps had trannies near this size; DH-500 (375@4 ohm) and that 70+ pound CV 600 (600@4ohm?).

Hamrules thanks for sharing the 250 rating for the balance. I'm definitely going the same path as you've been on--this one's worth time and effort. Yes, I'd already thought of new screws; the small back ones holding on the metal grill to the wood case are over-drilled and not holding.

The front plastic face I want to go with new glass (or at least new Lexan). Easy, the side front end comes off, it slides right in. Seems to have a second glass behind it, like my Technics tuner. Overbuilt in every way I can imagine.

And new lights, ultrabright LEDs for years from now when my eyes weaken. Maybe use that FM Dolby switch for a dimmer! :D

Your dual-mono TX-8500 is one of my favories too; like to hear you compare that one. I can't do a direct side-to-side any more because I traded mine (to another AKer :yes:), but I remember they may have a similar tone--at least at sane listening SPL's. :D


Iusnas-0009G I'm not trying to hijack your thread! :D We'll track down your cracklin'. Glad to know you tried it through the pre-out jumpers so you know your amp section is not on playin Cracklin' Rosie literally.
 
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I have the Lexan ready to cut, just did not do it yet. That's the final after all else is set. IDK, that Dolby switch does have some effect on the FM when you turn it on and off. Can't quite figure out what it's doing but it's doing something. I like the LED though I think I might have to figure that out instead before it get's closed up. Would be easy to put in a bridge rectifier where the transformer wires are for it at the junction and go from there.
 
Happiness!

Wonderful day indeed! Great time today shared on the Bench, tracing with a scope and calling board points /components. back and forth, out of a Super beautiful Japan print SM!
Many thanks to my Good friend Ken! Thank you! Ken for all your support/experience on this Fisher Receiver TS!
The Fisher Japan printed SM is as impressive as the RS1080 Receiver ! I was on the hunt/ hunch for a faulty Transistor. Scope and MM-Volt readings recorded today lean to support a pair of Faulty Transistors . I will order in and R&R to confirm!
Promise to post some stellar pics and the results after new parts are installed. Some of the SM also as it is so impressive!
It was a Spectacular Day!
 
pics you say?

Never seen a pic on the web with the tuner shield off so here's an exclusive:
Note the tuner pulley string has a smaller pully on the opposite side to alleviate sideways tension--very well thought out design :D

2-TunerVeract.jpg


The veractor adjustors are up from the bottom like a SX-1250. Less likely to have been meddled with before I got in there. I want to do the meddling meself...


1-TopViewInside.jpg
 
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