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7844 (view source)

Revision as of 23:23, 30 March 2015

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The 7844's CRT has [[distributed vertical deflection plates]].  It uses a number of custom ICs, such as [[155-0065-00]] and [[155-0059-00]] in the vertical amplifiers, [[155-0095-00]] in the vertical interface, [[155-0078-00]] in the  trigger selector, and [[155-0022-00]] in the horizontal interface. The horizontal and Z axis amplifiers are discrete.
The 7844's CRT has [[distributed vertical deflection plates]].  It uses a number of custom ICs, such as [[155-0065-00]] and [[155-0059-00]] in the vertical amplifiers, [[155-0095-00]] in the vertical interface, [[155-0078-00]] in the  trigger selector, and [[155-0022-00]] in the horizontal interface. The horizontal and Z axis amplifiers are discrete.


The power supply is a resonant switch-mode inverter with linear post-regulation, similar to the one in the [[7904]].  It uses the [[155-0067-02]] controller.  Despite having an SMPS, the 7844 is fairly heavy, which is mostly due to the second vertical delay line.  The delay lines need extra space and are located vertically to the right of the CRT instead of below the CRT as in other 7xx4s.
The 7844 is more complex than all other 7000 mainframes because vertical and horizontal amplifiers as well as the Z axis control boards exist twice, and there is an extra switching logic board.  As a consequence, verifying correct operation requires testing many possible combinations of settings – for example, a defect on the vertical switching board could cause a problem only in the case of both beam 1 and 2 using horizontal bay B, but not if beam 1 used A and beam 2 used B.
Moreover, calibration and adjustment is significantly more work than in a single-beam scope, e.g. CRT geometry trimpots need to be adjusted for matching both beams, not only for best geometry, and these adjustments slightly interact.
 
The power supply is a resonant switch-mode inverter with linear post-regulation, similar to the one in the [[7904]].  It uses the [[155-0067-02]] controller.  Despite having an SMPS, the 7844 is fairly heavy behause of the duplicate internal components, especially the second vertical delay line.  The delay lines need extra space and are located vertically to the right of the CRT instead of below the CRT as in other 7xx4s.


Unlike some other 7000 series mainframes with switch mode PSUs, the 7844 does have a fan.   
Unlike some other 7000 series mainframes with switch mode PSUs, the 7844 does have a fan.   
The 7844 is more complex than all other 7000 mainframes because vertical and horizontal amplifiers as well as the Z axis control boards exist twice, and there is an extra switching logic board.  As a consequence, verifying correct operation requires testing many possible combinations of settings – for example, a defect on the vertical switching board could cause a problem only in the case of both beam 1 and 2 using horizontal bay B, but not if beam 1 used A and beam 2 used B.
Moreover, calibration and adjustment is significantly more work than in a single-beam scope, e.g. CRT geometry trimpots need to be adjusted for matching both beams, not only for best geometry, and these adjustments slightly interact.


==Links==
==Links==
Retrieved from "https://w140.com/tekwiki/wiki/Special:MobileDiff/15419"

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