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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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Old 26th Sep 2020, 9:29 am   #1
vinrads
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Default Speaker protection circuit, which one?

I am thinking of fitting a protection cct on the Grundig R35 tuner amp, I see there are several on EBay anyone had experience buying/fitting one, Mick.
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Old 26th Sep 2020, 9:44 am   #2
Dickie
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Default Re: Speaker protection circuit ,which one ?

I purchased one that used the upc1237 chip and two OMRON DPCO relays a year or so ago from China. Slow delivery, of course, but it works fine.
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Old 26th Sep 2020, 10:18 am   #3
barrymagrec
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Default Re: Speaker protection circuit ,which one ?

The Vellman unit is well spoken of - I have no personal experience of it.

https://cpc.farnell.com/velleman-kit...tor/dp/HK00743
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Old 26th Sep 2020, 10:57 am   #4
vinrads
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Default Re: Speaker protection circuit, which one?

Thanks Barry I have ordered one , they look just the job , Mick.
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Old 26th Sep 2020, 1:27 pm   #5
Stockden
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Default Re: Speaker protection circuit, which one?

Interested to see that page 4 of the assembly instructions for the Velleman kit tell you to use "Thin raisin-core solder". I didn't know you could get that. Do they do apricot and prune as well ?

Hugh

Last edited by Stockden; 26th Sep 2020 at 1:30 pm. Reason: Typos
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Old 27th Sep 2020, 3:08 am   #6
BulgingCap
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Default Re: Speaker protection circuit, which one?

I have fitted this unit to all of my audio amps that had no protection, and several recent homebrew amps. I have tested the unit and it works as claimed. The chip appears to be very similar to the old Hitachi HA12002.
One point to note is that the unit needs an AC (or DC) supply of over 14V and under 24V due to the limits of the 7812 reg used for the relay supply. This supply needs to be independent to the amp supply AC, so in the case of one amp which used a toroid with only a 30-0-30 winding I had to use a tiny additional 15V transformer (salvaged from a wall wart.)
BC
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Old 27th Sep 2020, 8:51 am   #7
vinrads
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Default Re: Speaker protection circuit, which one?

Hi the I have ordered has a mains tx on board , Mick.
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Old 27th Sep 2020, 11:08 am   #8
BulgingCap
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Default Re: Speaker protection circuit, which one?

Hi Vinrads, Apologies - I didn't realise you were referring to the Vellemann kit !
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Old 27th Sep 2020, 11:44 am   #9
Goldie99
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Default Re: Speaker protection circuit, which one?

If you're pushed for space, and can tap into existing power supplies, there's a much smaller option available directly in Auss. - Project 33, on Rod Elliotts site.
https://sound-au.com/project33.htm

It's a bare pcb of the protection circuit only, so no transformer, no relay - you'd need to add your own separate relay(s). The overall quality & instructions are excellent, and it's particulrly useful where space is limited, as the pcb measures only ca. 6 X 3 cm.

Alan
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