Rotel RA-930AX - right channel down - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

hergest74 · 26th Jan 2023, 12:58 pm

ok, I have found the culprit (I think) The fuse that sits in front of the R channel speaker inputs has blown on closer inspection. The number of the fuse is T4L 250v and a funny symbol after that I don't recognise. I tested the R speaker channel of the remote side and the same problem so it's a channel issue, not a speaker terminal fault.

I would post an image of the fuse's location but no way of doing so here. What seemed to trigger the channel going was trying to test one of my Soundcraft Absolute 2 monitor speakers from my studio before I sell it as the Samson servo 170 amp that drives them has broken inputs (literally plastic falling to pieces) When I tried to connect the Spirit to the cable attached to the Rotel I did notice a little spark from the wire. But then again, it can't be the Spirit that caused it as why would it still work perfectly well in the L channel ?

Could this be the problem ? If so, does anyone know if these fuses are still available ? I notice a couple of others have not blown but show signs of a small molten blob of metal along the still unbroken wire.

The fuse in question is the right hand one with the red arrow in this image I found online. https://www.avforums.com/proxy.php?i...0254242310e53f

Station X · 26th Jan 2023, 1:04 pm

Have you tried swapping the blown fuse with the one from the left channel?

hergest74 · 26th Jan 2023, 1:16 pm

Quote:

Originally Posted by Station X

Have you tried swapping the blown fuse with the one from the left channel?

I just did thank you and it works! Why didn't I think of that

So now I need a few new fuses. Can anyone kindly advise the cheapest, fastest option if still available please ?

ajgriff · 26th Jan 2023, 1:21 pm

The fuse is a T (slow blow) 4A 250V. Readily available but check the length (mm).

Alan

hergest74 · 26th Jan 2023, 1:42 pm

Don't you mean a T4L 250v ? as this is the one that has blown. I have an identical looking spare fuse 250v with F2 at the beginning, not T. I take it this wouldn't be advisable ?

PaulR · 26th Jan 2023, 2:23 pm

You could use the other fuse to test the channel but that is a slow blow 2 Amp one. You really need slow blow (timed) fuses in the speaker circuit as its rating might be momentarily exceeded on loud passages at high volume. At 2A it is also rated at half the current so will blow more easily. It might be a good idea to try it temporarily on the affected channel to see whether there was a fault causing the original one to blow.

The voltage isn't important in this situation. A search for 4 amp slow blow or timed blow fuse on ebay will find you the right type.

Station X · 26th Jan 2023, 2:37 pm

The circuit in the service manual shows the SPEAKER fuses F601 and F602 as T4A.

The parts lists then shows 125V and 250V variants for these fuses.

https://www.amazon.co.uk/electrosmar.../dp/B0036A97KU

https://www.newbells.co.uk/t4a-4-amp...use-3413-p.asp

There are other sellers. Check the physical size of the fuse before buying.

PaulR · 26th Jan 2023, 2:54 pm

Quote:

Originally Posted by Station X

The parts lists then shows 125V and 250V variants for these fuses.

[

I wonder whether they are related to the mains voltages in different parts of the world. Those voltages might be more readily obtainable if they are close to mains voltage

Station X · 26th Jan 2023, 2:58 pm

I think that's probably it.

Obviously different fuse types are specified for the MAINS fuses.

hergest74 · 26th Jan 2023, 3:31 pm

Thanks folks. Just ordered a couple from Ebay.

26th Jan 2023, 12:58 pm	#21
hergest74 Tetrode Join Date: Jul 2020 Location: Manchester, UK. Posts: 52	Re: Rotel RA-930AX - right channel down ok, I have found the culprit (I think) The fuse that sits in front of the R channel speaker inputs has blown on closer inspection. The number of the fuse is T4L 250v and a funny symbol after that I don't recognise. I tested the R speaker channel of the remote side and the same problem so it's a channel issue, not a speaker terminal fault. I would post an image of the fuse's location but no way of doing so here. What seemed to trigger the channel going was trying to test one of my Soundcraft Absolute 2 monitor speakers from my studio before I sell it as the Samson servo 170 amp that drives them has broken inputs (literally plastic falling to pieces) When I tried to connect the Spirit to the cable attached to the Rotel I did notice a little spark from the wire. But then again, it can't be the Spirit that caused it as why would it still work perfectly well in the L channel ? Could this be the problem ? If so, does anyone know if these fuses are still available ? I notice a couple of others have not blown but show signs of a small molten blob of metal along the still unbroken wire. The fuse in question is the right hand one with the red arrow in this image I found online. https://www.avforums.com/proxy.php?i...0254242310e53f Last edited by hergest74; 26th Jan 2023 at 1:11 pm.

26th Jan 2023, 1:04 pm	#22
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: Rotel RA-930AX - right channel down Have you tried swapping the blown fuse with the one from the left channel? __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

26th Jan 2023, 1:21 pm	#24
ajgriff Nonode Join Date: May 2004 Location: Halifax, West Yorkshire, UK. Posts: 2,587	Re: Rotel RA-930AX - right channel down The fuse is a T (slow blow) 4A 250V. Readily available but check the length (mm). Alan

26th Jan 2023, 1:42 pm	#25
hergest74 Tetrode Join Date: Jul 2020 Location: Manchester, UK. Posts: 52	Re: Rotel RA-930AX - right channel down Don't you mean a T4L 250v ? as this is the one that has blown. I have an identical looking spare fuse 250v with F2 at the beginning, not T. I take it this wouldn't be advisable ? Last edited by hergest74; 26th Jan 2023 at 1:48 pm.

26th Jan 2023, 2:23 pm	#26
PaulR Dekatron Join Date: Oct 2003 Location: Southport Lancashire, UK. Posts: 3,236	Re: Rotel RA-930AX - right channel down You could use the other fuse to test the channel but that is a slow blow 2 Amp one. You really need slow blow (timed) fuses in the speaker circuit as its rating might be momentarily exceeded on loud passages at high volume. At 2A it is also rated at half the current so will blow more easily. It might be a good idea to try it temporarily on the affected channel to see whether there was a fault causing the original one to blow. The voltage isn't important in this situation. A search for 4 amp slow blow or timed blow fuse on ebay will find you the right type. __________________ Paul

26th Jan 2023, 2:37 pm	#27
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: Rotel RA-930AX - right channel down The circuit in the service manual shows the SPEAKER fuses F601 and F602 as T4A. The parts lists then shows 125V and 250V variants for these fuses. https://www.amazon.co.uk/electrosmar.../dp/B0036A97KU https://www.newbells.co.uk/t4a-4-amp...use-3413-p.asp There are other sellers. Check the physical size of the fuse before buying. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

26th Jan 2023, 2:58 pm	#29
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: Rotel RA-930AX - right channel down I think that's probably it. Obviously different fuse types are specified for the MAINS fuses. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

26th Jan 2023, 3:31 pm	#30
hergest74 Tetrode Join Date: Jul 2020 Location: Manchester, UK. Posts: 52	Re: Rotel RA-930AX - right channel down Thanks folks. Just ordered a couple from Ebay.