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kuhurdler
Joined: 28 Dec 2006
Posts: 2571
Location: Overland Park, KS
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JTS1957
Joined: 21 Jan 2009
Posts: 1331
Location: Far, Far Away
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 Posted: Mon Aug 03, 2009 10:47 am Post subject: |
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Transistor isolated from circuitry (or removed) & Meter on "Diode Test:"
B to E = infinity with leads one way - a ~.4 reading leads the other way;
B to C = infinity with leads one way - a ~.4 reading leads the other way;
C to E = infinity with leads either way. |
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chumba
Joined: 01 Jul 2009
Posts: 66
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| Posted: Wed Aug 05, 2009 8:22 am Post subject: |
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With Q801 removed & testing in diode mode:
C to E measures infinite with leads one way, & 0.6 with leads reversed and same for B to C.
B to E measures 0.25 with either polarity.
In R mode:
C to E measures infinite, & 1.6 Megohm with leads reversed and same for B to C. B to E measures 487 ohm with either polarity.
Should Q801 be replaced and not IC803? |
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JTS1957
Joined: 21 Jan 2009
Posts: 1331
Location: Far, Far Away
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| Posted: Wed Aug 05, 2009 12:28 pm Post subject: |
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Q801 is BAD - period. I'd get and replace both. When new transistor arrives compare new to old.  |
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chumba
Joined: 01 Jul 2009
Posts: 66
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| Posted: Tue Sep 15, 2009 5:46 pm Post subject: |
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Replaced Q801, but still no power up  with same clicking behavior as before. New Q801 measured infinite/0.68 from B to C and B to E and infinite/infinite from C to E (good measurements and different than the old, bad part). |
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JTS1957
Joined: 21 Jan 2009
Posts: 1331
Location: Far, Far Away
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| Posted: Tue Sep 15, 2009 6:21 pm Post subject: |
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What about IC803  |
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chumba
Joined: 01 Jul 2009
Posts: 66
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| Posted: Wed Sep 16, 2009 6:33 pm Post subject: |
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Have not replaced IC803. The DC voltages measure 8.7v on pins 1,2,4,& 5, and 327v on pin3 (essentially same as before changing Q801). Pulled the datasheet http://pdf1.alldatasheet.com/datasheet-pdf/view/38478/SANKEN/STR58041.html
which shows the equivalent internal circuit.
With IC803 removed in diode mode measures between pins
3 and 4: 0.5 and infinite w/leads reversed (should be a C-E junction)
2 and 1: 0.9 and infinite w/leads reversed (should be a C-E junction)
4 and 2: 0.01 and 0.01 (should be a C-E junction)
3 and 2: 0.5 and infinite (should be a C-B junction). |
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JTS1957
Joined: 21 Jan 2009
Posts: 1331
Location: Far, Far Away
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| Posted: Thu Sep 17, 2009 10:30 am Post subject: |
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A Collector to Emitter junction (with NO damper diode or any other internal resistors, etc.) on a DVM set on diode check should read INFINITE in both polarities - device OUT OF Circuit. Pin 2 to 4 alone is one junction B-E on transistor on the left (Unless you stiil have in circuit and something's in parallel?  |
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chumba
Joined: 01 Jul 2009
Posts: 66
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| Posted: Thu Sep 17, 2009 6:17 pm Post subject: |
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All these readings are with the IC completely removed from ckt. in DVM diode mode.
If pins 2 to 4 are a B-E junction, then the readings still look no good anyway, and also no good between 3 to 4 and 2 to 1 (if these are pure C-E junctions?). 2 to 5 measures 0.02 w/either polarity. Is this IC bad? |
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JTS1957
Joined: 21 Jan 2009
Posts: 1331
Location: Far, Far Away
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| Posted: Fri Sep 18, 2009 6:06 am Post subject: |
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| chumba wrote: | Should Q801 be replaced and not IC803?
| JTS1957 wrote: | | Q801 is BAD - period. I'd get and replace both. When new transistor arrives compare new to old. |
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