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Old 16th Jan 2017, 11:23 pm   #61
DonaldStott
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Default Re: Bush A.C.91

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Originally Posted by Voxophone View Post
Personally, I use these: http://www.ebay.co.uk/itm/10x-Capaci...-/190915805343

I hope this helps. The capacitor minefield can be a confusing place!
Thanks for the recommendation but when I clicked on your link the eBay page says: -

"This seller is currently away until 20 Mar, 2017, and isn't processing orders at this time. You can add this item to your Watch List to purchase later. "

Any other recommendations - I'd really like a site where I can pick from a drop-down list, 1 of those, 5 of those, 8 of those etc. etc.
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Old 17th Jan 2017, 9:53 am   #62
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Default Re: Bush A.C.91

It's usually Ebay, small independent supply companies or large supply companies, it's all down to how much you want to pay, availability etc, many such as RS Components, Farnell etc are easy to use, they use a filter system, click on the voltage, value, type etc and it will show what's available and what the minimum quantity is that you can order, make sure it's UK stock, if it isn't you'll have a wait and it's possible there will be a premium to pay, RS Components, Farnell etc will also in most cases have specification data for the component in question that you can download, a lot of suppliers don't provide that and as a consequence in many cases you wont know who the components are made by or if they conform to any safety or other standards.

At the end of the day 'tis up to you, we all have our favourite suppliers.

Lawrence.
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Old 17th Jan 2017, 9:55 am   #63
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Default Re: Bush A.C.91

A wide range of Capacitors, and other useful components, can be purchased from firms such as CPC, RS, and others. Details of these can be found via Google, and the parts can also be ordered on line via their websites. In some cases you may have to register and open an account, but many will supply on a 'payment with order' basis. Edit; Crossed with Lawrence.
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Old 17th Jan 2017, 10:39 am   #64
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Default Re: Bush A.C.91

Thanks guys - I already have accounts with RS Components, Farnell and CPC as a consequence of my other "electronic activities"

Just wondering if there was a preferred supplier that people used?

I'm also now a BVWS member but haven't used their services for components??
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Old 17th Jan 2017, 10:43 am   #65
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Default Re: Bush A.C.91

As Lawrence has said, Farnell stocks similar capacitors. In the 'film capacitors' section of their website apply filters for 'axial leaded' and '630V' and you should see some similar to the ones in my link. Usually they will be described as 'PET' or 'Polypropylene' but don't worry about the material. The value and voltage rating are usually all that matters.

Edit (post crossed). I tend to get mine from the eBay seller I linked to or Farnell. I've used RS once or twice for other types of caps but not the 630V types. I'm sure they do stock them however. Crinklewood Electronics seems to be spoken of highly on here: (https://www.cricklewoodelectronics.com/Capacitors.html) I've not used them personally but they do stock capacitors as well as a few other bits useful for valve radios.

Last edited by Voxophone; 17th Jan 2017 at 10:56 am.
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Old 17th Jan 2017, 10:43 am   #66
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Default Re: Bush A.C.91

http://www.bowood-electronics.co.uk/...acitor-c-4_147


https://www.cricklewoodelectronics.c...00-630VDC.html

Amongst others.

Lawrence.
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Old 17th Jan 2017, 5:43 pm   #67
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Default Re: Bush A.C.91

Someone needs to put me out of my misery ...!

Will this do as a substitute for C30 0.1μF 500V X-class capacitor:-

https://www.cricklewoodelectronics.com/CXR100N.html

And what about C3 0.005μF 500V Y-class capacitor?
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Old 17th Jan 2017, 6:18 pm   #68
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Default Re: Bush A.C.91

Yes, that X2 rated capacitor will be ok.

If they don't list a Y type then they probably don't do them.

Personally I would go with a larger supplier such as Farnell etc, they are likely to have everything you need, when I used to use them I would order up a pile of common value capacitors, resistors etc, also wire, solder, spare soldering iron bits and anything else I was likely to need, box full of stuff arrives, job done.

Other's might have other ideas.

Lawrence.
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Old 17th Jan 2017, 6:32 pm   #69
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Default Re: Bush A.C.91

Thanks again Lawrence - Cricklewood seem to have everything I need apart from that Y-class capacitor?

I'll have another go at Farnell but just too many choices for me in terms of voltages (AC, DC), types, materials etc. etc.

I note that there is quite a bit of crumbling wiring on my Bush AC91 - what gauges of wire would be standard. I note there are some short runs of what looks like co-axial cable as well?

Started cleaning the chassis last night so I'll need to stock up on cotton buds. I promise to lie low for a while once I get all my required components ...!
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Last edited by DonaldStott; 17th Jan 2017 at 6:33 pm. Reason: Typo
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Old 17th Jan 2017, 6:43 pm   #70
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Default Re: Bush A.C.91

For 0.005uF Y class cap suitable Farnell part would be

http://uk.farnell.com/kemet/pme271y4...rad/dp/9717552

which is 0.0047uF Y2 rated.


For 100nF X class suitable Farnell part would be

http://uk.farnell.com/kemet/pmr209mc...00r/dp/9717412

Neither is the ONLY suitable part Farnell stock but it's a single option for each!


The ultimate narrower down on the huge Farnell choice of capacitors is to pick from the interference suppression film capacitor range. ALL of these will be either X or Y rated and there's not a huge choice in the specific values you need. For these classes of capacitor you don't need to worry about their DC ratings, they are all rated for at least 250Vac and more particularly meet the required safety standards for their intended application either across L-N (X) or from L or N to any accessible conductive part (Y).
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Last edited by Herald1360; 17th Jan 2017 at 6:49 pm.
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Old 17th Jan 2017, 8:39 pm   #71
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Default Re: Bush A.C.91

Good news guys as I've just placed a large order with Farnell - thanks for all your help and guidance.

I promise to stay off the Forum for a few weeks and just get on with it ...!
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Old 17th Jan 2017, 10:05 pm   #72
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Default Re: Bush A.C.91

Don't do that- we're as interested in progress as in sorting out problems!
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Old 21st Jan 2017, 12:07 pm   #73
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Default Re: Bush A.C.91

Just a quick update to show progress so far.

Attached photos show the upper side of the chassis, valves removed and basic cleaning started. Highlights some dodgy wiring and grommets that need replacing on the valve caps and IF cans! I'd rather not open those cans but fear I may have to!

Last picture also shows the rather rusty wire tuning drive mechanism which is giving me cause for concern as it looks and feels very fragile.

As usual any advice and/or guidance will be welcomed?

While I'm here I need advice on how/where to measure the Output Transformer which I can now get access to.

Pictures of the underside coming later.
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Old 21st Jan 2017, 12:20 pm   #74
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Default Re: Bush A.C.91

To measure the output transformers resistance connect one probe of your meter set to ohms on the tag that's connected to the anode of V4, probe on the other tags, one of them should give a reading of 500 ohms approx, that's the primary winding, secondary windings rarely fail but to check it disconnect one of the speaker leads from the transformer tag then one probe on that tag and then on the other tag that feeds the loudspeaker, should be 0.75 ohms approx.

Lawrence.
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Old 21st Jan 2017, 6:29 pm   #75
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Default Re: Bush A.C.91

O.k. - struggling to get any readings whatsoever from the Output Transformer but have the feeling that I'm connecting to the wrong tags - hopefully!

I've found the tag that connects to the anode (pin 3) on V4 which is the yellow wire in the attached photo - one probe from the meter to this tag but which tag for the other probe?? Have I missed something that would be obvious to an experienced restorer?

Thanks to everyone for their patience and ongoing support ...
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Old 21st Jan 2017, 6:35 pm   #76
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Default Re: Bush A.C.91

You should get a resistance reading from one of the other tags, if not then that would indicate the transformers primary winding is open circuit, double check to make sure, but first make sure you have continuity from the tag you've described to the anode of V4.

Lawrence.
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Old 21st Jan 2017, 7:09 pm   #77
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Default Re: Bush A.C.91

Open circuit output transformer primary on the DAC90/90A is a very common fault IMHE, more likely to be open than not. I expect the transformer in the 91 is the same part - it looks the same in your pictures - with a similar failure rate
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Old 21st Jan 2017, 7:09 pm   #78
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Default Re: Bush A.C.91

Quote:
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You should get a resistance reading from one of the other tags, if not then that would indicate the transformers primary winding is open circuit, double check to make sure, but first make sure you have continuity from the tag you've described to the anode of V4.
Thanks Lawrence - we have continuity between the Output Transformer tag and pin 3 of V4 so the yellow wire is o.k. I have all valves removed at present.

I note that we have C28 (Fixed tone correction capacitor) wired across the Output Transformer tags - if that is leaky (or dead) could it account for the open circuit?
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Old 21st Jan 2017, 7:16 pm   #79
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Default Re: Bush A.C.91

Not normally if it was short circuit, that capacitor though, needs to be on your replacement list, replacement should be a min of 630 volts DC rated, I used to replace them with 1,000 volt DC jobs because sometimes high voltages can be developed across the primary winding.

Lawrence.
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Old 21st Jan 2017, 7:28 pm   #80
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Default Re: Bush A.C.91

I have a 630v replacement in my bag of goodies from Farnell so I'll remove the existing capacitor and see what happens.

Looks like I may be placing another Post in the Wanted section - how common are Output Transformers or are there modern equivalents?
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