Fisher FM 200 B Questions

monoethylene

monoethylene

Active Member
Hi,

I am new here and my name is Philipp. In a few days I will receive a FM 200 B from Fisher and I am sure that I will have a lot of questions :).

The Fisher should arrive in a good cosmetic condition with all tubes inside and knobs.

Nevertheless I am living in Germany and I ve read that the De-emphasis is different between USA and Germany.

Can I change the de emphasis of the unit??

Can you guys give me some advices for good indoor antennas??

I will show photos as soon as the unit arrives about cleaning and so on :)

Stay tuned..

Philipp
 
Is this FM200B a U.S. unit, being shipped to germany??? or is it one that has been in europe all the time.


De-Emphasis is not normally changeable (no switch to push). You would need to figure out the math and apply it to a couple of capacitors and resistors in the FM circuit. I have had a couple of receivers where they had adjustable de-emphasis and fiddled with them and didn't hear any real difference. That and Fisher was still experimenting with Multiplex at that time and de-emphasis was generally lower than 75us. closer to 60us. I'd recap the unit 1st, then listen to it. If it sounds muddy in the highs in FM ONLY, then the de-emphasis needs to be adjusted. It'll have to be done at a shop.

At least try a "T" dipole depending on how close you are to the stations. You may need an outdoor antenna.
 
Don't really know the MPX section of the FM-200B but if it's anything like the Fisher 400 it's suggested that you change R222 & R223 to 4K7 for stereo de-emphasis. R28 to 30K for mono.

Here's a article that discusses it for the Fisher 400:
http://audio-nirvana.fortunecity.net/pag_eng/fish400g.htm

Here's part of the schematic on the 400 where R222 & 223 are:


attachment.php



I've sent several 400s from the States to the UK and to be honest never changed those resistors and the FM sounds great. I guess I'll try it and see if it sounds better - can't imagine that!
 

Attachments

  • 400-multiplex.jpg
    400-multiplex.jpg
    98.2 KB · Views: 224
Thanks for the replies :).

Actually it is a unit shipped from the US to me (Germany).

I ve already read some things about the changing of the resistors and so on but I may go into it a little bit deeper.

First the unit has to arrive, then cleaning and measurement of the caps and then listening :) and asking again..:)

Cheers,

Philipp
 
To clarify the Part numbers Bruce is using, R28 is the part # in the 48001 and up schematic on the 400. If you use the "starting 20000" or the "20001 to 29999" version of the 400 manual, the part # is R63. The Multiplexer versions on all the 400 is the same (ie: mpx 65). If the 200B's mpx unit is a MPX 65 you can change R222 & 223 to 4K7. the 200B Service manual is here....... http://tubesrit.com/audio/thumbnails.php?album=28 It's jpg pages. click on each page to enlarge it then download each page.

It looks like R104 is the "R" to change, at least to me it is. Check on it tho.



I changed the resistors and caps in my 400 and didn't notice any change at all. I've got a 800-C. and gonna change out the mpx unit for a better looking one. the only thing I'm changing on the mpx65 before it goes in is the 1uf 350V cap. Other than that, nothing is getting changed.

I'd give it a listen 1st. it may or may not sound ok depending on whether it's been recapped.

Larry
 
Thanks a lot :)

I already have the manual of the 200B. Nevertheless it is the manual from 30.001 to 49.999 and my unit is higher (sth in the 50000). I checked the schematic with the one of "Bhamham" and the Rs are the same (R222 and R223) of the LCR network which goes to the output channels A and B of the MPX connections.

Right now I dont find the R104. I only find a hint with the words LAST R104 C??

Philipp
 
R104 is on the main schematic. Follow the line from pin 1 of the mpx up and to the right. you'll see the mpx test socket. Just below that is R104.

Larry
 
Today I received my unit finally :)

Right now I am cleaning it and dissassembled the front plate and so on.

In another thread here in the forum I ve read that the glass is really sensitive. In detail, I mean the Fisher logo and the scale. Is this right?

Another question I have is, if it is possible to glue the festoon bulb again because mine is broken :( Further it seems that I only have one festoon and not two like in the other thread. I am talking of this thread

http://www.audiokarma.org/forums/showthread.php?t=406997&page=3

The other one is a fuse instead of the bulb ?? Is this correct?

Here are some pictures:

img6203i.jpg


img6190m.jpg


img6186g.jpg


Cheers,

Philipp
 
Festoon bulbs in that size and voltage are no longer are available, at least in this country. What we usually do is to us 8v fuse lamps. If you fit a short piece if copper tubing from a hobby store over the ends, it fits and works perfectly. Looks like someone fit a fuse lamp in your unit. If you order them, they come in different length, so measure your festoon. One side of the festoon is painted and the painted part faces away from the dial glass. I put a thin piece if index card next to mine to direct the light as I was afraid paint might burn from the heat. Looks just like new.
 
monoethylene said:
In another thread here in the forum I ve read that the glass is really sensitive. In detail, I mean the Fisher logo and the scale. Is this right?
Click to expand...

Best to test a small area around the edge first. On my last two Fisher 400 dial glass I've used an ammonia/water mix with no problems and they look fantastic. I was amazed at how tough the paint was. A few days ago I read where someone cleaned a 500C dial glass with plain water and his lettering just wiped away and he was looking for a replacement. So be very careful.
 
Thanks a lot for the replies. I will have a look for the bulbs.

Meanwhile I ve finished the cleaning.

Before:

img6183b.jpg


After:

img6219z.jpg

img6220n.jpg


Cheers,

Philipp
 
WOW!

What a major difference!

Can you please detail the process and fluids you used to clean?

Really nice work!
 
Thanks a lot.

Actually I used an electrical teethbrush and hot water with dish liquid. After that I dryed it with a microfiber cloth. After that I used Never Dull but before I ve tried the letterings and at the chassis the letterings are really good, at least in my case :)

The houses of the tubes are also cleaned with Never Dull. The tubes itself are only cleaned with a towel on the top because the lettering will remove easily.

Nevertheless the flywheel has changed within the cleaning process :( :( Dont ask why :).

How can I readjust it?

Cheers

Philipp
 
Wow! I won't show mine (lots of corrosion and brown spots on the chassis)...

It must go back on the workbench soon as it has distortion so I need to finish my restoration and replace the remaining brown caps (and fix a precedent mistake: a 8uf electrolytic I wired backward two years ago. Maybe it's why it doesn't sound so good! :))
 
Please can you help me and tell me how is the plug for the 72 ohm antenna connection called??

The reason is that I am looking for an adaptor to European standard.

Cheers

Philipp
 
Last edited:
You must log in or register to reply here.

Similar threads

E
Fisher 400 deemphasis help!
Replies
19
Views
2K
dcgillespie
dcgillespie
audmod01
FM-200-B Acquisition
2 3 4
Replies
66
Views
2K
audmod01
audmod01
RUmad
FM-200-B
2
Replies
34
Views
969
RUmad
RUmad
thefragger
Fisher R-200/FM-200-B Tubes?
Replies
12
Views
2K
thefragger
thefragger
TENER
Fisher X-202-B and FM-200-B I picked up
Replies
10
Views
371
tonyg88
tonyg88
Back
Top Bottom