jim_at Posted April 13, 2010 Share Posted April 13, 2010 Hi, I'm not sure if anyone will know the answer to this but it's worth a shot! One of the valves has blown in my Hi-Watt bass custom 200 head, and upon replacing the valve with a new KT88 I have read I have to re bias the amp. I need to find out what the base plate voltage that the amp should be, how where / how to use the trim pot in the amp that I have to adjust to get it in the right range on a volt meter. If anyone has ever re biased an amp before and can offer any advice, I'd love to hear it. Thanks Jim Quote Link to comment Share on other sites More sharing options...
Mr. Foxen Posted April 13, 2010 Share Posted April 13, 2010 Does it have individual bias on each valve? If so guess you could check the rest. If not, then probably supposed to get a matched set. Quote Link to comment Share on other sites More sharing options...
jim_at Posted April 13, 2010 Author Share Posted April 13, 2010 Valves work in pairs, right? I've ordered a pair, so hopefully if I just change the pair of which the individual broken valve is connected to, it should be ok? Rather than replacing all four valves. Quote Link to comment Share on other sites More sharing options...
Mr. Foxen Posted April 13, 2010 Share Posted April 13, 2010 [quote name='jim_at' post='804704' date='Apr 13 2010, 11:30 AM']Valves work in pairs, right? I've ordered a pair, so hopefully if I just change the pair of which the individual broken valve is connected to, it should be ok? Rather than replacing all four valves.[/quote] In this amp they work in pairs, but if there is only one bias control, you are adjusting the bias for all the valves. Quote Link to comment Share on other sites More sharing options...
jim_at Posted April 13, 2010 Author Share Posted April 13, 2010 I think there are individual bias pots on this amp. I just don't know what reading I should be trying to adjust to! Quote Link to comment Share on other sites More sharing options...
27 frets Posted April 14, 2010 Share Posted April 14, 2010 [quote name='jim_at' post='804667' date='Apr 13 2010, 11:00 AM']Hi, I'm not sure if anyone will know the answer to this but it's worth a shot! One of the valves has blown in my Hi-Watt bass custom 200 head, and upon replacing the valve with a new KT88 I have read I have to re bias the amp. I need to find out what the base plate voltage that the amp should be, how where / how to use the trim pot in the amp that I have to adjust to get it in the right range on a volt meter. If anyone has ever re biased an amp before and can offer any advice, I'd love to hear it. Thanks Jim[/quote] I'd contact Hiwatt, as they are building basically the same amps now [url="http://www.hiwatt.co.uk/contact.aspx"]http://www.hiwatt.co.uk/contact.aspx[/url] There is an option on that page for sending technical queries Quote Link to comment Share on other sites More sharing options...
jim_at Posted April 14, 2010 Author Share Posted April 14, 2010 Thanks, I have already emailed them but no response as yet. It was a new build 2-3 years ago anyway! Quote Link to comment Share on other sites More sharing options...
umph Posted April 14, 2010 Share Posted April 14, 2010 take it to a tech and ask to sit in its a 5min job. Quote Link to comment Share on other sites More sharing options...
Pentode Posted April 14, 2010 Share Posted April 14, 2010 [quote name='umph' post='806201' date='Apr 14 2010, 04:20 PM']take it to a tech and ask to sit in its a 5min job.[/quote] That Sir, is very sound advice! Quote Link to comment Share on other sites More sharing options...
Beedster Posted April 17, 2010 Share Posted April 17, 2010 [quote name='umph' post='806201' date='Apr 14 2010, 04:20 PM']take it to a tech and ask to sit in its a 5min job.[/quote] Yep, that way it gets done right and you know how to do it next time. I see working on gear as being a bit like plumbing, get it done professionally first time around, but in doing so, learn how to do it yourself next time Gotta go, I can hear some water leaking upstairs C Quote Link to comment Share on other sites More sharing options...
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