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New to Tubes...800c score...help restore.

Warning...Brasso and probably too hard of a rubbing :nono: did break apart some of my lettering on the back side.
Not much, but enough to bum me out a bit. :tears:
But those areas do shine something nice...a "silver lining" I suppose.
Not sure how to proceed with the rest. :scratch2:

Still no word on restore kit delivery...anxious.
Will keep studying.
martin
 
If there is no lettering in the area, use what you want. The brasso is a bit stronger (due to ammonia and abrasives), but Maas or Flitz are good choices where there is lettering. Plain water and ammonia (6 to 1) with a soft toothbrush works well also.

Larry
 
If you have a HOBBY TOWN nearby, check out the rub on letters in the Train section. There used to be a font there that was really close in size. Once rubbed on, clear coat with Nail polish.
 
Okay...
For those looking for misc items to restore your Fisher, this is what I have found.

For knob caps there are several at auction if you type in "fisher caps". I hastly purchased some that are stamped (unknowingly) from sheets of brass. They look well enough if not right next to each other. They have a rounded edge, not the sharp crisp edge like the originals There is another seller in Hong Kong. His look to be more original. Before you purchase, press the seller to inform you if they are stamped from sheets or machine turned.

For side lamps, at auction, type in "7V fuse lamps". Mine are in transit and will let you know how they work. I did purchase some 12V LED festoons, but the 7V just wasn't enough to light them up fully. Couln't find any 7V LEDs festoons.

The MAAS polish is really good stuff. Still be careful and wipe softly. Use alot of clean soft rags. My lettering has held together really well. But I must tell tell you that my backside had a pucker factor of 10 when polishing around the Fisher logo. I don't really endorse this pratice as some lettering on other Fishers may fall apart just by simple dusting. Enter at your own risk.

My Restore kit with Sonicaps came today from Metalbone. Shipped on saturday, arrived on monday. So tonight I have been reading and studying the instructions. There are about 36 components to be replaced. Tomorrow I'll prep the work space (man...this place is a mess) and make sure I have everything I need, and then review some more. Don't know when I turn the iron on.

Out with the old :thumbsdn: and in with the new :thmbsp:!

The mullard I bought at auction for 9 bucks total tested as "replace". At least it not totally shorted like it's predecessor. Will probably replace again.

Martin
 
Okay guys, I'm about ready to start my restore.
Since mine is a working 800c, is there any testing I should do to give me a pre restore reference point?
martin
 
marloubow said:
Okay guys, I'm about ready to start my restore.
Since mine is a working 800c, is there any testing I should do to give me a pre restore reference point?
martin
Click to expand...

Use a digital camera and take lots of pictures before you start in case you get stuck later. Only takes a minute or two
 
Last night I finished preping for the restore and finishing a few loose ends.
I finished polishing the chassis and brass on knobs. Deoxited the remaining tube sockets and gave a light sanding to the tube pins.
Since my output tubes were already out I thought I would go ahead and start removing the pin 5 ground connections and replace with the 10 ohm resistors. Though my math is terrible, one equation became quite clear...
removing any leads from Fisher terminals=PITA.

So what is the prevaling thought/feelings about just clipping old leads and just soldering to the existing "glob" of solder that is already present?

Meanwhile I'll just keep working on removing the pin 5 grounds.

Martin
 
removing any leads from Fisher terminals=PITA.
Click to expand...

lol, welcome to the club... i have a asortment of dental tools I like to use. lately i have been favoring one in particular which has a flattened football shaped end. it allows me to get under lead and then i rotate to sort of pry away from terminal. it can get frastrating but remember all the terminals are easily replaced as long as you have a source.

i like to cut away what i do not need or intend on reusing. seems fisher normally did not leave a whole lot of extra wire so cutting those away can be a bear but beats melting the jacket.
 
After each phase of component replacement, is it okay to test changes thru a pair of headphones, seeing how I have a functioning unit?
 
This is a great thread. I recently picked up a good working Fisher 400, and the person I got it from tossed in for free one of Metalbones upgrade kits for it which he never got around to installing because the 400 sounded great as it is. I'm trying to muster up some courage to install it, as I'm a complete newb at swapping out capacitors, etc, although I've soldering microphone elements into my harp mic shells.
I'll be checking in daily to learn what I can. Thanks fellas! :thmbsp:
 
Okay...
I just finished phase one of the metalbones restore.

1) replaced the 5 pin to ground with the 10 ohm resistors so to protect the output tubes during the course of the restoration. tested okay!

2) Checked for voltage at the filter can capcitor. Checked again. Sketched out the rectifier/capicitor circuits and made compairisons with the provided instructions.

3) Clipped out the filter cap and removed the rectifier.

4) Mounted new rectifier in hole closest to 15 ohm sandcast resistor. I soldered the AC lines and neg (-), (which I had splice on about 3" of wire to get back up to the (-) on the new filter cap) before I mounted it to chassis.

5) twisted both (-) leads on new filter caps together and soldered together.
I used a little DS sticky tape to hold them together and put a bit on the inside of the can clips so they would hold still.

6) resoldered all leads from rectifier to cap according to sketch and confirmed with instructions.

7) The resistor R119 is listed as a 5.6k. Mine tested in circuit at 4.08K and 5.58k on the bench. I was given 3 options in the kit. 2.7k, 3.3k and 4.3k. Went with 3.3 for the time being. I tied this connection in last and away from the other (-) leads so as not to disturb those solder joints in case I needed to change out later with a different value to get the output to -17 volts or what ever the prevailing wisdom dictates.

I tested thru headphones and realize that I'm going to have to set up some good speakers to really get a better idea if any changes take place.

Still plays and no magic smoke (it is the life blood of all electronics).

Just realized that I forgot to replace C92. Was so involved in the completion of the PS that I didn't notice I had a part left over.

Maybe tomorrow we'll get to play again.

Martin

ps bolted some 1/2" ply to sides of chassis to protect everything and give stability as I turn it from position to position. See below

pss. wife and I's 27 anniversary today...very cool. She tolerates me well.

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Thanks Kory
Yes audiodon, that is what I intend to do. Just finished phase 2 and tested thru HP first and then when everything looked good, I hooked up the JBL 4410a's. It seems to have changed for the better, but I don't know if anything that I've done so far would make a difference sonically or not.

Question...where along this restore should I look for a noticable change in the sound?

Tonight was pretty straight forward.

1) I sketched out the circuitry and made special notice of the diode's "polarity". CR6 and CR7. Double checked my diagraming against instructions. Clipped and desoldered old leads and installed new diodes.
Starting to put a bit of deoxit on terminals before soldering. Seems to help.

2) Replaced caps C92, C104 and C110. A lead of each diodes share a terminal with C104, so clean it well. There is alot of bulk there to flow solder thru.

3) I installed the thermister between the power cord terminal and the on/off switch lead that runs in the flex EMT to the front of the unit. On mine it's the brown weave fabric over insulation. It needs to be in the open because as I understand it, it gets hot.

As usual there is a little trepidation in powering it up after each phase. So check, check and recheck your work.

Tip...
When reusing existing stranded wire, it helps to deoxit and tin the strands.

An aside... The 7V fuse lamps work (meaning they light up), but are loose in the contact clips...think I'll solder mine in. :screwy:

I am trying to be helpfull with out giving too much info. Louis at metalbones has put alot of work into his kits so they are easy to follow, especially for the noob (like me). So for me to reproduce verbatium here what he has done wouldn't be right. Thanks Louis. :thmbsp:

May start phase 3, "Amplifier Signal Path" tonight...yum yum.

martian

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Okay…
I just finished the amplifier section of the 800c. Phase 3.

Replaced a total of 10 capacitors. C99. C101, C44, C46.

C116 and C117 have (+) and (-) orientation. So check and recheck.

Capacitors C16, C17, C18 and C16 were upgraded in the kit to Sonicaps. Audiodon has also recommended the 600 volt .1uf Russian green K42Ys or the silver K40Ys.

Most of the replacements were fairly easy. But some of the old leads attached to tube pins were the 3rd component down. So instead of risking a broken pin with a lot of tug and pull, I did one of two things.

First was to desolder the entire pin and while it was still “fluid”, gently push all existing leads down the pin to create space on top for the new component. Of course you would clip the old lead as close to the pin as possible.

Second was to clip the old lead as close to the component body as possible. Then wrap (curl) the new lead around a small stiff wire to create a “pigtail” (see photo below) that would slide over the old clipped lead. I know in some circles this is frowned upon, but the site of a broken pin would be worse by far IMHO.

Tested and sounds great. Will need help later when I get to biasing.

Not much else. Things get a little tougher in the next 2 phases. Mostly because of cramped spaces.

Martin
P.s. I could use a little feedback on all of this. Is this working for you guys or am I just taking up space?

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Just finished the AM/FM signal path this morning.

Replaced 7 capacitors. C49, C60, C64 and C73 are all pretty easy, but consider the sequence of installation as the area to work in is confining. Again a sketch was made of all circuitry because I removed C64, C60 and C73 all at one time.

C65 is polarity oriented. Because of its proximity to the output tubes, it is susceptible to high temps and is recommended that it be moved to the diode switchboard. This I had to think about a while.

C67 was simple swap out. Just make note of polarity before removing.

C111 has given me pause also, seeing that (+) goes to ground. But the schematics confirm this.

There is so much of this that I don’t understand…which is why I have a “kit”.

But I know more than I did 3 weeks ago…thanks.

My head hurts.

Martin

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