View Single Post
  #21   Report Post  
Posted to sci.electronics.repair
John Robertson John Robertson is offline
external usenet poster
 
Posts: 907
Default Marantz Model 19 Scope

On 2019/04/29 10:28 a.m., three_jeeps wrote:
On Friday, April 26, 2019 at 1:22:32 PM UTC-4, wrote:
Does anyone know anything about these ? I know the basics but there are details missing from the print, LIKE THE PINOUT of the CRT !

I can see though (thank you Drs Budrous and Stewart) so I can see the thicker wires, those are pretty much at cathode potential, -500 volts. I can also find the deflection plates and with the centering make the DC voltages equal, still no display.

Unless there's something I missed I need to get into the grid and focus voltages and if those are all there, the CRT is bad ?

From what I hear you would need a SWAT team and a bunch of automatic weapons to get a replacement CRT. Even people with experience on these things, how many receivers had built in scopes ? I saw one in another brand once but can't remember what it was, maybe a Kenwood ? Other than that only Marantz and then even very few models.

I got the other problems fixed, it had a fault on the one power amp board and a bad transistor on the tone amp board which is by the way stuck to the chassis with double sided foam tape ! For what they charged fro these things, foam tape ? And you should see the PITA it is to remove, I was thinking "This board it gonna break", but it didn't.

What you really need is a Fein cutter with an L shaped blade. (they are normally used to cut windshields out of cars)

Anyway, thanks in advance for anything useful on this matter. It makes a big difference in the value of the unit.


Have you tried boosting the filament voltage ? For one it is the best way to extend the life of a CRT, rather than rejuvinating. I wouldn't recommend that for a CRT unless it was in a TV, the color CRTs pull quite a bit of current and guess where it all comes from - the cathodes.


A common trick to boost filament voltage as well as grid voltage was through the use of aftermarket transformer 'CRT boosters'...Basically a dongel that was inserted between the crt socket and the crt pins. Been so long, I forget how they were sized, and am sure you would be hard pressed to find one nowadays...


These were a simple step-up auto-transformer designed for 50/60Hz. I
have one or two lying around my shop and any old radio/TV museum would
have a pile of them I'm sure.

John :-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."