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Help identify diode!
Help identify diode!
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Old 20th June 2018, 04:18 PM   #1
hollowman is offline hollowman  United States
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Default Help identify diode!

The diode (at position "183" of attached PCB image. It's sitting vertically, between two jumpers, next to jumper 219, parallel to vertical black chassis divider):

It's small, white with a black (cathode) and another green band.

It sits on the -5v rail, near the 7905 reg. One side (cathode) ties to -5v pin of a TDA1541 dac. The other side goes to -5v rails/pins of various servo chips/transistors.

The diode drop about 0.5v .So, I'm assuming it's being used to "further drop/regulate" voltage to the TDA1541A (where the -5 rail measures -4.5).
On the anode side of the diode, all the servo components get all -5.0v.

Problem is, the TDA1541A has a min. -5v rail requirement of -4.5v. And I've seen this value as high as -5.6v on good, working, factory-original CD players.

Again, help me identify the diode (parameters) so I can look for a replacement that has lower Vfd.
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File Type: jpg PhilipsCD60_diode_183.JPG (289.6 KB, 128 views)
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Last edited by hollowman; 20th June 2018 at 04:29 PM.
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Old 20th June 2018, 04:29 PM   #2
Elvee is offline Elvee  Belgium
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It is definitely from Philips, thus from the body colour it is either a BAWxx or a BATxx.
Since it is a small body, it must be a BAT, and from the color code (gray/green), it is a BAT85, a small schottky diode.
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Old 20th June 2018, 04:32 PM   #3
leadbelly is offline leadbelly  Canada
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Help identify diode!
Can you explain what problem occurred or what is not working on the device? It doesn't really make sense that you are needing to change the diode yet it does not appear to have failed.
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Old 20th June 2018, 07:30 PM   #4
Mooly is offline Mooly  United Kingdom
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Help identify diode!
Quote:
Originally Posted by leadbelly View Post
Can you explain what problem occurred or what is not working on the device? It doesn't really make sense that you are needing to change the diode yet it does not appear to have failed.
I think he is hoping for a flash of inspiration from someone as I get the feeling hollowman isn't to impressed by the replies so far received in another thread/s. But I could be wrong...



First it fell off the table, well I think it fell off a table although it may have had a soft landing (the diode puts in an appearance around post #76):
Philips (Marantz) CD-60 not spinning up

Replacing CD laser -- laser power and/or focus trim

Better laser amp transistor than BC338?
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Old 20th June 2018, 09:01 PM   #5
hollowman is offline hollowman  United States
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The Marantz CD60 serv. man. shows the position that diode is in (183) to be a jumper, not a diode. Methinks it was some sort of last-minute tweak to the TDA1541's -5v power-rail.
Also, it may serve to "isolate" the TDA1541 from other ICs powered by the 7905 reg.

Quote:
Can you explain what problem occurred or what is not working on the device? It doesn't really make sense that you are needing to change the diode yet it does not appear to have failed.
I laid all out in the OP, dude. I know, I know ... the habit nowadays is TL;DR.
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Old 20th June 2018, 09:18 PM   #6
leadbelly is offline leadbelly  Canada
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Help identify diode!
You laid it out? Into conspiracy theories much?
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Old 20th June 2018, 10:24 PM   #7
JMFahey is offline JMFahey  Argentina
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Well, he already said that falling off the table was not that important, and that he does not see anything broken, so ....

EDIT: as of:
Quote:
I laid all out in the OP, dude.
that will certainly motivate members to try to help
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Last edited by JMFahey; 20th June 2018 at 10:27 PM.
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Old 21st June 2018, 01:58 AM   #8
hollowman is offline hollowman  United States
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Quote:
Originally Posted by JMFahey View Post
Well, he already said that falling off the table was not that important, and that he does not see anything broken, so ....

EDIT: as of: that will certainly motivate members to try to help
Please point to the exact post where I supposedly said the above.

The CD60 did not fall off a table; it tipped off to its side (about 1 foot) from a low shelf on to a matted/carpeted floor. And I suggested that was not "important"? Really?

Mooley, in his summary post above, was POORLY summing up the etiology of the CD60 thread.

In any case:

The... Philips (Marantz) CD-60 not spinning up
... thread is long, has a lot of detail, and not bedtime reading. But if you're a techie, and are up to it, it may be worth a lookover. Warning: you may find it humiliating, humbling or disturbing
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Old 21st June 2018, 02:04 AM   #9
hollowman is offline hollowman  United States
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Quote:
Originally Posted by Elvee View Post
It is definitely from Philips, thus from the body colour it is either a BAWxx or a BATxx.
Since it is a small body, it must be a BAT, and from the color code (gray/green), it is a BAT85, a small schottky diode.
Thx.

Again, it's not in the PDF schematic. The 183 position is shown with a jumper (not diode). Must be some kind of last-min. addition, never making it into the "final draft".
Now all I need is on of these guys with the min. Vfd possible (Wiki suggests this maybe 150mV as min. for Schottky ???).
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Last edited by hollowman; 21st June 2018 at 02:08 AM.
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Old 21st June 2018, 06:56 AM   #10
Mooly is offline Mooly  United Kingdom
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Help identify diode!
Vfd varies tremendously in relation to the current being drawn through the device. The diode was obviously built into the final design, and the final design also used a -5 rather -6 volt initial supply.

Altering the original design isn't really the way to fixing your fault imo, although trying things can sometimes be a useful handle into a problem.

Have you tried shorting the diode to see if the fault changes ?

You could also use a normal diode to 'lift' the -5 volts to around -5.6 and see if that has any effect.

At the end of the day, your working player was fine until it fell, and after which it was faulty........
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