Fisher 800-T SS Need Help

T

themadreason

Member
Scroll down for the short version and Nude Amp Pics if you do not want the epic sonic journey of my eight fold path to the old Fisher 800 T.

I am new to the vintage electronics hobby. I decided to build a small kit amp before tackling any restorations. I just learned to solder by building a K12-G kit from S-5 electronics.

Hopefully, I am now worthy of what is undoubtedly a masterpiece of vintage electronics....

The Fisher 800 T.

(If the prices on Ebay say anything! I definitely need all the help I can get to not butcher this wonderful old amp!!)

This bad boy has been sitting around my parents garage for years. I remembered it from my childhood, but never appreciated what it was until quite recently. Being the first amplifier that I heard as a kid.

Sensibly, when I heard Jimi Hendrix on this K-12 amp, I freaked out. What other ancient analog devices have I missed out on?! Immediately, my mind reached out to the distant memories of the old dusty Fisher. I immediately went to rescue it from my parents garage.

I asked my parents if I could have it to work on. My Mom told me a good story. The amp found its way to America in the possessions of a Vietnam veteran, who bought it at his base's PX. The amp toured with the man and came back with him. My Mom bought it off of him as a friend of a friend for a measly sum in the late 70s.

Nude Pics are in PT II for all of you amp pervs out there....
 
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The PICS!!! Part II

At some point the amp caught fire!!! This happened on the power switch board. A repair man bridged over the burnt circuit, and hard wired the amp in the on position. He replaced the cord with one that had a switch wired into it. A rabbit ate through the power cord, and this was the end of the Fisher's first life.

Now there are some busted and swollen caps. What should I use to recap the power board? One big Syncro is leaking, and I want to keep the two caps matched, so I am planning to replace them both.

Crap, I need to restart to windows to upload these PICS.

One moment.
 
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Fisher 800T Pics

Here is my amp.
 

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That's a nice receiver, good as it gets for early Fisher SS. Worth the effort to put it right. I'd think that Nichicon axial caps available at Mouser would work fine on the power supply board.

I don't know what happened here -

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Resistor legs soldered together? That's not right. Looks like the service manual is gonna be tough to find. I'm not sure if 500T service data is usable.

BTW, welcome to AudioKarma!
 

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More Pics

One more wide shot of the bottom.

Things that I know are wrong. I have a lot of experience with computer hardware, so I know a bad cap when I see one exploded. I can see the big filter cap leaking. What I simply cannot find are good replacements for them. I am not optimistic about reparing the big scortch on the bottom to original spec. The amp worked in this state until a rabbit bit through the power cord with his NASTY BITEY TEETH!

Those diodes look really rough. I would also like to put in new ones when I pull the board out. What modern equivilant Diodes should I use?

The service manual speaks of testing the amp in stages with a volt meter. Can anyone tell me how to do this? I have a Fluke 117 multimeter, a soldering iron, and I plan to get ahold of a solder vaccum for this work.

Any suggestions or advice are greatly appreciated.
 

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I have the 500 TX service manual. I am a bit leery of using it. If they changed the circuit enough to take Euro current, I doubt a great deal of the material that pertains to the very power switch board that I would like to fix.
 
Fire Damage

Here is the top side of the fire damage.

I also need a screw in rubber foot for the bottom. Does anyone know of a good place to find something that at least matches?
 

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The 800-T is a 500-TX. The later service manual actually says "and 800-T".

The proper manual is a must on the early SS pieces- they made so many changes that you want to make sure you have the manual that matches your serial number block.

Having restored several early SS pieces myself- they are a lot of work. Every electrolytic should be changed, socketed transistors (if so equipped) should be cleaned, and the old grease should be cleaned off and replaced on the output transistors.
 
OK. What kind of thermal paste should I use? I think that I have some arctic silver 5 laying around from my last PC build. Is there a different formula that would be better for this old amp?
 
The 500TX and 800-T are THE SAME UNIT. The 800T was the Multi Voltage version of the 500TX. the manual you have is correct. There is a section on the main schematic that shows the 800-T transformer setup.

Those caps are RADIAL! They have a 3rd Stabilizing leg so they didn't glue them down. I thought I sent the S.M. copy to Jailtime for inclusion to the AK DATABASE. I'll send it again. I just hot glued mine down on my 500-TX.

Looks like the Power supply board cooked off and burned the amplifier board a bit. It's Repairable. Replace all of the resistors, caps, and diodes (ncluding the zeners) on the power supply board to start. It might surprise you and come ot life.

BUILD A DIM BULB TESTER. YOU'll NEED IT! If you don't you run the risk of a repeat fire in it.

Did you get the remote control for it? The remote is Standard on the 800-T and optional on the 500-TX.

It's not an easy one to recap. But it is one of the easier of the FISHER's to do. If you need any help, PM me. Mine is still fairly fresh in my mind. I didn't do a thread on it, but I DO have some pics.

http://www.audiokarma.org/forums/showthread.php?t=346927 Link to a recent 500-TX recap thread


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IIRC I used Panasonic FC caps for the 2 Filter caps. 3300uf by 75V. Replace the 1000uf/50V next to the amp with a 2200/63V. The rest of the caps were Nichicon UPW's in the power supply and UKL's in the Signal path. Films were replaced with either DME's or Lemon drops (yellow axial's Cornell Dublier). Might be a couple of WIMA's in there too. Didn't have to replace any of the transistors. You will have to removethe outputs and at least test them. MJ15003/15004 or MJ15015/16 would be the output replacements, made by ONSEMI. Sold @ Mouser for between $3.50 and $4.00 each. The 15/16 would be a bit of overkill, but won't hurt.



Larry
 
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themadreason said:
OK. What kind of thermal paste should I use? I think that I have some arctic silver 5 laying around from my last PC build. Is there a different formula that would be better for this old amp?
Click to expand...

DON'T use Arctic silver ...only use the correct stuff .computer stuff is conductive .
 
Zener Diodes

What kind of diodes did you use to replace the ones on the switch board?

What would be the best way to fix the burned traces?

I would like to bridge over them with a small PCB project board. I plan to solder the two big resistors on either side of it, and put the two smaller missing resistors in series on the new PCB to avoid whatever nightmare is waiting for me on the bottom of that circuit board.

The repairman who fixed it before hard wired this amp on. I noticed that he cut a small resistor on one board on the top of the amp. He cut a few wires on the power switch board. How do I restore this on and off function of the amp to its original state? I will post pics.

I imagine that the first repairman bridged over the trace because something is terribly wrong with it. I will post an update when I get the board out.

What about the fire damage on the top of the amp?

Thanks in advance for the help.

Also, what is a dim bulb tester? I assume that I connect a light bulb into the outputs from the circuit board?

- Stephen
 
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Gimme a day or so Kyle.

Thermal paste. As Jailtime said , or the Silicone based stuff @ Radioshack works.
Bottom Feet, Ace Hardware. Brown or white hard plastic in pairs.
DIODES: 1n4007. IIRC there is a 25V 1W and 14V 1W Zener in the power supply.

PARTS WISE. Everythign you need for the power supply (resistors, caps, diodes, etc.) you can get @ Mouser. Use the Service Manual to get the specs, then do the look ups @ mouser. Unfortunately I didn't keep the BOM or parts list from Mouser. All the parts should run you between $7.00 and $10.00 + shipping (power supply only). The rest of it is 99% caps. but you'll need to take apart some stuff on the amp to test. One thing at a time.

When you get your parts list made up, post it and I'll vet it for you, ok it it or make appropriate changes.

Larry
 
themadreason said:
What kind of diodes did you use to replace the ones on the switch board?

What would be the best way to fix the burned traces? if they haven't lifted from the board, check continuity. If ok, clean them up and use them. Bridge with small pieces of wire (insulated) soldered to the good ends of the trace

I would like to bridge over them with a small PCB project board. I plan to solder the two big resistors on either side of it, and put the two smaller missing resistors in series on the new PCB to avoid whatever nightmare is waiting for me on the bottom of that circuit board. Before you go and do that, pictures of the traces would help. Looks like the Large resistor on the lower side of the pic was put in as a stopgap. It's way TOO Large. And I can't wrap my head around it right now. Tell me the part numbers (according to the schematic). Mainly it looks like scorching and smoke damage so far, but the trace side needs to be seen.


The repairman who fixed it before hard wired this amp on. I noticed that he cut a small resistor on one board on the top of the amp. He cut a few wires on the power switch board. How do I restore this on and off function of the amp to its original state? I will post pics. [/b] Lets get everyone on the same page for terminology. The two boards you are describing are the POWER SUPPLY and the MAIN AMPLIFIER. There is no power switch board. Looks like the "repairman" jumpered the switch. Find the leads from the power switch. One will be on pin 9V and one on 9M. If not which ones. Look at the board diagram and compare the traces too. He may have made trace changes. [/b]

I imagine that the first repairman bridged over the trace because something is terribly wrong with it. I will post an update when I get the board out.
pictures of the complete trace side, close ups of each 1/2 of the board, trace side.
What about the fire damage on the top of the amp?
Cross that bridge when we get to it. BEFORE YOU POWER IT UP, I'll figure out which leads to the amp I want you to pull and insulate to keep it from frying anymore.
Thanks in advance for the help.

Also, what is a dim bulb tester? I assume that I connect a light bulb into the outputs from the circuit board? It's a current limiter that put in series between the wall and the unit being tested. Lights up a lightbulb rather than your unit. Search in the DIY Forum and build one. Real easy and cheap. Plus it will help keep the fisher from self destructing anymore.

- Stephen
Click to expand...

Larry
 
Pics

Here are some other strange things. The resistor looked like it was cut under magnification. The ends were wedge shaped. There was also a cut white wire on the power board.

I see the jumpers, and I assume that the original on switch was tied into the volume knob? The knob does not click on or off.
 

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The green wire needs to come out. You need to look at mine and see the wires on 9V and 9m. Find the one that was removed from 9M (it goes to the switch and is red also. He may have jumpered it as the switch may be bad).

change your profile to show your location. If you're in Asia and I'm on the East Coast of the US, one of us ain't gonna get any sleep.

Lets concentrate on one thing at a time. Start with the power supply board. And go from there.

That resistor needs to be replaced. But we'll get to that later.

This ain't gonna be an overnight thing. It's gonna take a few weeks. You rush it, and the FISHER will rebel and up and quit.

Pull out your manual and open it to the power supply board drawing. Go around the board and mark EACH wire on a pin with a piece of tape and it's pin location. then remove the wire from the pin. Remove the screws and put them in a bag and mark it. Remove the board from the plastic squeeze pins(needle nose pliers work for this.) then flip the board over and take pictures of the overall trace side, and 1 of each 1/2 of the board. I'll use those to mark up here with corrections. DO NOT REMOVE, MODIFY or install parts until I OK it. You want a working piece of gear, not a smoking pile. I'll help as much as I can within my capabilities, but you need to NOT get ahead of me.

Larry
 
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