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Author Topic: R 2005D Motorola service monitor help  (Read 8601 times)
KA5IPF
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Posts: 1043


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« Reply #30 on: December 15, 2012, 03:38:48 PM »

"Never say, 'never'"...

<g>

Left off the "I" never use sockets! YMMV

Clif
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WB6DGN
Member

Posts: 619




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« Reply #31 on: December 15, 2012, 04:10:45 PM »

Quote
That's where the 2600 series shine.

Yeah but in my case there was always a 2670 sitting around in the Mobile Shop if I really needed it.  Almost never did, though.  I hated that delay on the scope and spec. an. though.  Seemed 3 or 4 times longer than the HP I have at home and I'm not crazy about it.
Tom
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NJ1K
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Posts: 369




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« Reply #32 on: December 15, 2012, 05:06:35 PM »

"Never say, 'never'"...

<g>

Left off the "I" never use sockets! YMMV

Clif

Huh??
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N3DT
Member

Posts: 668




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« Reply #33 on: December 18, 2012, 04:06:05 PM »

Saga continues.  Got parts from Mouser, replaced ICs that I thought may be bad and nada.  Same thing, nothing changed.  I've got one more to replace, a 7405N hex inverter.

Funny thing is the 339 works on my breadboard, but not in the circuit.  But it may be the hex inverter dragging it down, that's my next try.

Anyone know where to get a cross reference on a DS75361N?  Dual TTL to MOS driver.  I doubt if it's bad, but wouldn't hurt to have a couple in case.
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N3DT
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Posts: 668




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« Reply #34 on: December 28, 2012, 01:53:34 PM »

Looks like I've got it.  Apparently when I replaced a bad diode on the LVPS A5, I made a solder bridge across two others, so it was still in current lockout.  Trouble is the only way one can see it's in that lockout mode is on A4 U8 pin 13 or U2 pin 10.  If it's high, it's locking out the PWM.  In the meantime I pulled U8, the lockout IC and wiped out the AC switching FETs.  So I found the other short on the LVPS A5, replaced the FETs, the correct voltages came up on the A2 through A6 power supply boards, re-seated all the boards and it powered up, I have display, the buttons work and things appears normal.  I'm going to leave it on for a while before I button it up.

I really doubt if I could have fixed it without the schematics, unless I was really lucky.

Woo, Hoo.

Many thanks to NJ1K for his help.
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K7KBN
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Posts: 2838




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« Reply #35 on: December 28, 2012, 03:44:11 PM »

I think "hex inverters" are covered in the second year at Hogwarts ...  Grin
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73
Pat K7KBN
CWO4 USNR Ret.
N3DT
Member

Posts: 668




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« Reply #36 on: December 28, 2012, 06:03:34 PM »

The hex inverters were working fine and still are.  Actually everything in the control board was doing exactly what it was supposed to do.  When I removed the overcurrent IC, that caused more problems.  There was just not enough explanation, at least for me, as to what is happening on the control board, in the Motorola manual.
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