maplin only do a 1k ohm and a 5k ohm so I'll pick up both in the hope one will be suitable. if i wind the 5k half way back from full that could would work. presumably i can get it to measure 2k
Try a search on Maplin for Potentiometer 2k5. They list two. You can search store stock for either.
5k could make the setting very critical with a tiny movement causing a large change in current. If you do fit a 5k then just set it to 5k initially. That would give a zero bias state.
A 1k would work but it would need one of the series resistors changing to say 680 ohm and leaving it in place. That would give a 680 to 1680 adjustable resistor which should be in the right range. Its more trial and error though. The preset would be set to 1k initially which (hopefully) would be at a point that would give zero bias.
5k could make the setting very critical with a tiny movement causing a large change in current. If you do fit a 5k then just set it to 5k initially. That would give a zero bias state.
A 1k would work but it would need one of the series resistors changing to say 680 ohm and leaving it in place. That would give a 680 to 1680 adjustable resistor which should be in the right range. Its more trial and error though. The preset would be set to 1k initially which (hopefully) would be at a point that would give zero bias.
thanks a lot mooly. just got a work call to make here then I'm off to maplin for the pot
You will get more stock/choice from UK suppliers like:
Rapid, RS, Farnell, CPC
and all of them are likely to be cheaper.
Some do next day delivery, and some are free if you exceed the minimum order value.
the other bits have come from farnell i just had today largely free and wanted to get today
I've removed the drivers, the outputs and the two 0.22 ohm resistors and all the NFR [!] resistors measure correctly.
out of time tonight, thanks for your help folks. progress report tomorrow
Hi.
Recently I let someone borrow my Cyrus 1 for a charity event and unfortunately it returned as a dead Cyrus. I did a visual check and replaced a 3.15A fuse, only to discover that one of the output transistors was shorted. Trying to find a replacement has lead me to some interesting sites, without much luck. Then I found this thread and have been amazed by the help being given to someone who wants to learn by doing. I'm an advocate of learning by failing, though I don't actually see it as failure.
I've registered and read all the posts and am about to put together my own shopping list. I just wanted to say 'thanks' to all who have been helping because it's going to help me no end. Also, it's a change to read comments that actually inform and share, rather than recommend that one finds an expert to do it for you.
Recently I let someone borrow my Cyrus 1 for a charity event and unfortunately it returned as a dead Cyrus. I did a visual check and replaced a 3.15A fuse, only to discover that one of the output transistors was shorted. Trying to find a replacement has lead me to some interesting sites, without much luck. Then I found this thread and have been amazed by the help being given to someone who wants to learn by doing. I'm an advocate of learning by failing, though I don't actually see it as failure.
I've registered and read all the posts and am about to put together my own shopping list. I just wanted to say 'thanks' to all who have been helping because it's going to help me no end. Also, it's a change to read comments that actually inform and share, rather than recommend that one finds an expert to do it for you.
I too have been bowled over my the help given to me when I know very little but am willing to learn and read around the issues.
I hope when (not if) my Brother's cyrus 1 is working again , those that have helped me will get a sense of satisfaction from that and that I , in return , can be of assistance to other fans of sick old gear
Thanks for the welcome.
I've collated all the info and will be slowly making my way through all the advice in the hope that some will be retained. I get the distinct feeling that first off I'll have to make a bulb limiter. Reliance on visual location of the smoke source may be frowned upon.
I really like the concept of passing on the knowledge.
I've collated all the info and will be slowly making my way through all the advice in the hope that some will be retained. I get the distinct feeling that first off I'll have to make a bulb limiter. Reliance on visual location of the smoke source may be frowned upon.
I really like the concept of passing on the knowledge.
really wasn't difficult to make one. just a switched socket and a bulb holder wired in series with the live supply to it. into the switched socket i can plug in a normal 3-pin mains to iec kettle lead. Watching the filament briefly glow then dim I found strangely pleasing / reassuring. I felt like I'd calmly regained control of an unruly puppy