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Marantz 4400 CRT replacement by 2bp1

N

novanec

New Member
Hi

I have a marantz 4400, the CRT is damaged, is the 50tb1, but I could be replaced using the RCA crt 2bp1, works perfect, without modifying the circuit or voltages, only changing the connector pins, attached diagram. This is achieved crt on ebay at a price of 30 dlls, is very easy to get, unlike the original which cost 300 dlls, and is very difficult to achieve, is 2 inches in diameter by 6 long. I hope to serve.

http://medisoft.site40.net/2bp1marantz.html

2bp1.JPG

mar1.jpg

mar2.jpg

mar3.jpg

mar4.jpg

mar5.jpg

mar6.jpg
 
Last edited:
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:tresbon: Wow - awesome tip!! There are quite a few of us 4400 owners out there with some pretty good burn-in on our scopes. For $30-40 bucks and some minor rewiring we'd be back in business.

Thank you!

(PS>> Possible to fix your picture links so we can have a look?)
 
Very cool....Thanks....

I have two Russian replacements.... But the RCA is cheaper and easier to get....

Johnk
 
Fair Radio Sales in Lima, Ohio USED to have a pretty good supply of 2BP1s. I haven't seen a catalog of theirs in a long time, but I'd bet they still have 'em. They catered to the ham/Burgeoning Mad Scientist crowd.. The Audiophools kinda looked down their noses at 'em, but they never knew what they were missing, IMHO..
 
This would be good news to those who need it, maybe also works in the similar 2110 and 2130 tuners with scopes?
 
mech986 said:
This would be good news to those who need it, maybe also works in the similar 2110 and 2130 tuners with scopes?
Click to expand...

Don't see why it wouldn't work. My 2110 used the 50TB1. And the 4400 is packed much tighter, so space shouldn't be an issue either.
 
Updated mine but, used seperate filament transformer since the amperage requirement is much higher.
camman
 
Marantz 4400 2BP1 Scope tube Substitute?

> Updated mine but, used seperate filament transformer since the amperage
> requirement is much higher.

Camman: Was this reference to the 2BP1 tube Novanec refers to ?

Has anyone else tried this substitution ?
 
I believe the 50TB1 has a 160ma heater rating vs. 600ma rating for the 2BP1.
Haven't heard of anyone smoking the stock transformer heater winding but, I decided to just be safe and add seperate 6.3v 1 amp transformer.
camman
 
Marantz 4400 scope tube sub

Camman,
Thank you for shooting over that response so quickly !
I have 4 questions....

1. How did you know the current requirement of the 50TB1 Filament ?

2. Did you find the 50TB1 Pinout Specs somewhere ??
If so, will you share the source?

3. I assume you used Novanec's pin out modification illustration ?

4. Now that you have done the modification, how does it compare to the original performance wise ?
 
I looked at my files but, can't find where I saw the heater spec.
The pinout is contained in the 4400 schematic.
No, my conversion was been done 2-3 years ago.
Changed my green crt to a "russian" blue phosphor crt. Works fine but, not quite as bright.
Please no worry about questions, glad to help!
camman
 
Marantz 4400

Hey Guys,
Sorry for the delay getting back to you both.
I didn't realize that there was a second page !!

Thank you both for the replies! They answered many questions.
Novanec: The pdf and gif images were GREAT and will be a great help
:thmbsp:

Camman: Yes, I have the 4400 schematic but I don't remember the pinout specs being there. Novanec's pdf helped out in this regard.

Also Camman:
How did you find a blue 2BP1 ????
I thought they were only available in green....

If you guys ever need help trouble shooting the 4400 or a 4300 I have outlined quite a number of issues on the schematic. I bought them new in 1976 and have serviced them many times over the years. If you plan to keep the receiver for the long haul, I can be reached directly: NetcomD(at)aol.com
 
Zillandia,
The pinout spec's I thought you referred to was the pin# and internal connection.
The blue phosphor CRT is a Russian tube 5LO38M. Very difficult to locate these days. Found mine after an arduous Internet search. :boring:
camman
 
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