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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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14th May 2018, 11:42 pm | #1 |
Octode
Join Date: May 2003
Location: Belper Derbyshire
Posts: 1,910
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BA148 diode. Can I use a 1N4007 in its place
Good evening,
Having issues and looks very much like this diode is conducting in both directions. It is a single diode rectifier off a winding on a LOPT to produce the A1 and focus voltages. A 10uF capacitor on the rectified output side was changed as the diode was getting warm and no EHT was produced. Removing the capacitor the EHT sprang back to life and the diode was cold. Replacing the 10uF with a new cap resulted in exactly the same as before. There is no loading on this circuit other than a 10 megohm pot. Therefore I believe the diode is the culprit here The PIV for this diode is 300V. Should a 1N4007 diode be ok in this position. I have a couple of BYW96E (1KV 3A) diodes somewhere could one of these be used? Many thanks, Christopher Capener
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Interests in the collection and restoration of Tefifon players and 405 line television Last edited by high_vacuum_house; 14th May 2018 at 11:48 pm. |
14th May 2018, 11:47 pm | #2 |
Octode
Join Date: Jan 2014
Location: Oban, Scotland, UK.
Posts: 1,118
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Re: ba148 diode. Can I use a 1N4007 in its place
1N4004, 5, 6 or 7 will work fine
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15th May 2018, 12:27 am | #3 |
Dekatron
Join Date: Nov 2011
Location: Surrey, UK.
Posts: 4,385
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Re: ba148 diode. Can I use a 1N4007 in its place
IN400x are slow turn-off, and in an HF supply will be inefficient and may upset the circuit operation. BA157, BA158 would be a more usual modern substitute and cost pennies but the fast-recovery BYW96E would be worth putting in if you can locate one and ought to be bullet-proof here.
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15th May 2018, 12:39 am | #4 |
Dekatron
Join Date: Apr 2012
Location: Worksop, Nottinghamshire, UK.
Posts: 5,549
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Re: ba148 diode. Can I use a 1N4007 in its place
UF4007 should work. They are fast enough for SMPSUs.
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15th May 2018, 7:22 am | #5 |
Dekatron
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 7,061
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Re: ba148 diode. Can I use a 1N4007 in its place
Agree Refugee and turretslug, the types they suggest should be fine.
Try a 1N4007 only if you don't mind doing a few replacements if it doesn't work. The slow turn-off will be inefficient at best, and might take out the drive transistor or reservoir capacitor at worst. |
15th May 2018, 11:01 am | #6 |
Octode
Join Date: Jan 2014
Location: Oban, Scotland, UK.
Posts: 1,118
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Re: BA148 diode. Can I use a 1N4007 in its place
I tend to purchase the UF4*** series as a matter of course these days. 'Same' device but faster. I should have mentioned this at the start.... sorry.
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15th May 2018, 11:08 am | #7 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,801
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Re: BA148 diode. Can I use a 1N4007 in its place
The 1N400x series tend to turn off with a snap, radiating a lot of RF interference.... that stuff we moan about coming out of billions of SMPSs.
Counter-intuitively, using fast diodes makes things cleaner. David
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15th May 2018, 11:10 am | #8 |
Dekatron
Join Date: Jun 2016
Location: London, UK.
Posts: 3,687
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Re: BA148 diode. Can I use a 1N4007 in its place
Very true with the 1n400x's. You have to stick a cap across them to shut them up!
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15th May 2018, 4:30 pm | #9 |
Octode
Join Date: May 2003
Location: Belper Derbyshire
Posts: 1,910
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Re: BA148 diode. Can I use a 1N4007 in its place
Well I fitted a new BYW 96E diode and a new 10uF 450V capacitor and this has sorted out the A1 and focus supply. The old diode once removed conducted in both directions!!.
We now have EHT in a fashion and light on the CRT though looks like there is a breakdown in the EHT overwind. The 0V wire out of the overwind has corroded away where it goes into the potting compound. Many thanks for your help. Christopher Capener
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Interests in the collection and restoration of Tefifon players and 405 line television |