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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
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15th Sep 2019, 6:55 pm | #1 |
Hexode
Join Date: Apr 2008
Location: Ramsgate, Kent, UK.
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KW2000 Unobtainium Parts
I'm trying to sort out some spare parts for my KW2000E to pack away with it when we move home, but have come across a few items for which I can find no data and hence no possible replacements. Does anyone have data sheets, know the ratings of, or equivalents to the following:
BY236 Diode BY238 Diode BYX36-150 Diode 8SC20 Varicap Diode 3A05 Diode/Rectifier (I suspect 50 PIV 3A, but could be wrong) Thanks. Adrian |
15th Sep 2019, 7:18 pm | #2 |
Dekatron
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Re: KW2000 Unobtainium Parts
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Frank |
16th Sep 2019, 1:02 am | #3 |
Nonode
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Re: KW2000 Unobtainium Parts
The 8SC20 is actually the 6.8SC20 by International Rectifier Corp.
Data I could find on it is limited, so if anybody has an old IRT databook (1985 ish). 50pF@0.1V to 2.5pF@-200V yes, that is minus 200V And Motorola lists the MR501 as the equivalent of the 3A05 which as you suspected is 50v 3A |
16th Sep 2019, 6:12 pm | #4 |
Hexode
Join Date: Apr 2008
Location: Ramsgate, Kent, UK.
Posts: 252
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Re: KW2000 Unobtainium Parts
Thanks for the info chaps.
It is somewhat amazing that the 'older' active parts i.e. valves are all readily available with data sheets a plenty to down load, but when it comes to the solid state parts they seem to be almost unobtainable both in parts and data. Adrian Last edited by RF Burn; 16th Sep 2019 at 6:17 pm. |
17th Sep 2019, 12:20 pm | #5 |
Dekatron
Join Date: Dec 2007
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Re: KW2000 Unobtainium Parts
I seem to have misplaced my ECA replacement guides, but they almost certainly have the basic data on the three BY.... types mentioned. Also, an ultrafast 1000V 3A rectifier such as the UF5408 is an almost universal replacement for hundreds to thousands of older diode types.
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17th Sep 2019, 1:13 pm | #6 |
Dekatron
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Re: KW2000 Unobtainium Parts
Ther following information might be of help Adrian:
BY238 Datasheet avaiable here: https://www.web-bcs.com/diode/dc/ba/.../ba/BY238.html BY238 diodes available from Little Diode’s ebay shop at £3.09 post-free: https://www.ebay.co.uk/p/BY238-Silic...am/25012056300 BYX36-150 Data here: https://www.silicon-ark.co.uk/datash...et-mullard.pdf Diodes available here, but it looks like just a 1A 600V rectifier diode – nothing special. (EG 1N4007 etc): http://www.weisd.com/test/GenericPar...d1=BYX36%2F150 3A05 is equivalent to Motorola MR501. See Motorola equivalents catalogue here: http://bitsavers.trailing-edge.com/c...iodes_Data.pdf The MR501 is in stock at Little Diode eBay shop at £3.79 post free: https://www.ebay.co.uk/p/MR501-Silic...kaAj9MEALw_wcB Good luck in your quest.
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17th Sep 2019, 1:31 pm | #7 |
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Re: KW2000 Unobtainium Parts
THe varactor will be the difficult one.
Remember you can parallel them and add their capacitances if you need to. But varactor types have been vanishing for years. For some capacitance ranges there are now no longer any parts made. David
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17th Sep 2019, 1:57 pm | #8 | |
Heptode
Join Date: Dec 2014
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Re: KW2000 Unobtainium Parts
Quote:
The trouble with varactors in parallel is that they have the problem that the minimum capacitance is also doubled. For a large value varactor (say 100pF) I have noticed that the minimum capacitance value is highish anyway unless getting very close to maximum reverse voltage. |
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17th Sep 2019, 3:01 pm | #9 |
Dekatron
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Re: KW2000 Unobtainium Parts
If that varicap diode is in the RIT circuit it may no require a large change in value.
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Frank |
17th Sep 2019, 7:58 pm | #10 |
Heptode
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Re: KW2000 Unobtainium Parts
Sorry Frank. I was being general rather than specific as I found them less amenable than mechanical circuitry so sharing my findings.
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18th Sep 2019, 2:04 am | #11 |
Nonode
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Re: KW2000 Unobtainium Parts
A little more digging on the varicap shows references to it as far back as 1967, so it goes back a fair way (no extra data at this stage though).
However, if you look at the schematic of the KW2000E, you will find a different varicap on the actual drawing - 1N4803 - even though the 8SC20 is listed in the parts list. May be another avenue to explore for a substitute. |
18th Sep 2019, 6:46 am | #12 |
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Re: KW2000 Unobtainium Parts
Varactors in parallel to make larger values, if you keep all the same type, at least retain the capacitance ratio. All capacitances scale up by N.
The age of this part puts it before the hyper-abrupt varactor diodes came along with their higher capacitance ratios. The -200v capacitance spec fits as well. David
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