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thepigeon 20th January 2012 06:23 PM

Kent SL 21 Tube head need help!!
So I just bought a Kent SL 21 amp head on eBay and realized I have no clue what the output of the amp is in ohms so I can wire my speaker cabinet properly. Here is the best picture of the schematics I can come up with. I haven't been able to find anything about these amps online but its a 2 - EL84, 2-12ax7, what appears to be a 6v4 rectifier amp. Not sure on wattage either so if anyone can help me out with that one I would appreciate it. It is missing its fuse and from what I gathered from my little knowledge of tube amps and stuff is that I need a 3AG 2 Amp Fast blowing fuse? Not sure if that's right either. Really any info anyone might have on helping me out would be great thanks.

If the photo link doesn't work I can email it. Not great at this whole forum thing lol.

kent amp schematics | Flickr - Photo Sharing!

Jebem 20th January 2012 10:39 PM

I don't know that amp in particular, however from a pair of EL84 in Push-Pull we can expect a minimum of 5 Watt in Class A and a maximum of 15 Watt in Class B. It really depends on the BIAS operating point used for the output tubes.

You can connect a 8 ohm impedance loudspeaker to that amplifier, as this is the standard value to be used when we don't have any other clue.

As for the fuse, it depends on the mains supply the amplifier is designed to operate with (110V or 220V). But I would say that an 1 Amp slow blow fuse or a 2 Amp fast blow are acceptable values, as this is a low power amplifier.

thepigeon 20th January 2012 11:02 PM

Thanks. I ended up putting the 2 A fb fuse in it and hooking up my 8 ohm speaker and it sounds alright. Really quiet though. The pots are gonna have to be changed because they all are really rough. All the tubes light up. At first it had a lot of crackle and pop and then it just came alive. Probably the first time its had power in a long while. Its really quiet and kind of muddy so I am thinking maybe a bad cap or two. So I think I am either going to take it to a local music store to have a cap job and see if that helps or try and convince one of my friends who knows about electronics to help me with it. Need to change out the 2 prong cord first and then check everything. But hey it works. It has tremolo on one of the channels, but I think it requires a footswitch to work, because I couldn't get anything out of it with just the knobs. I'll post some pictures here tomorrow hopefully. This is a unique little amp from what I can gather. I have found only one picture of a combo version of it online and it didn't have much on it. No info pages anywhere. Hopefully I can get it back up and running in full working order. If I can get it sounding good then I am probably going to build a cabinet for it and possibly a new speaker cabinet as well. Its in kinda rough shape the way it is now. Thanks again for your help.

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