[GreenKeys] M33 SMD Boards...

[Jack]

There was a similar board on a 35ASR electrical service unit that 

would regularly go bad. When a new board was plugged in, a

certain resistor would immediately go up in smoke...then the board

would work fine. I think the board had something to do with the 

keyboard and TD signal routing.

 

Jack K2TTY

 

NNNN

 

 

 

From: GreenKeys [mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of Kenneth Gartland
Sent: Thursday, April 13, 2017 9:36 AM
To: greenkeys <GreenKeys at mailman.qth.net>
Subject: [GreenKeys] M33 SMD Boards...

 

Hi all!

 

Resistor heating and circuit board charring is commonly

encountered on these SMD boards...

 

Teletype Corp'n was well aware of this problem, and later

versions of these boards had the resistors (The affected ones),

raised above the circuit board to allow a little airflow underneath...

 

When I was shop repairing these older boards, I would 

always raise the resistors above surface...

 

They do run quite hot, and I recall seeing some of the very

early production boards with little strips of insulating

material underneath the resistor bodies...

 

I still think best bet is to raise the height of the affected

resistors, likely you will have to physically replace them

as the leads will now be too short!

 

Cheers!

 

Ken

VE3-HMQ

i-Telex 61663

 

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