taximan Posted August 26, 2010 Report Share Posted August 26, 2010 Hiya, My sammich was going great guns and then blue spark,puff of smoke and a dead bc337...its actually split open. Can any of you knowledgeable folks tell me what else I should check? Replacing the transistor is no big deal but I am wondering if anything else could be damaged in that bit of the circuit. any advice appreciated cheers Paul Quote Link to comment Share on other sites More sharing options...
Wilba Posted August 27, 2010 Report Share Posted August 27, 2010 This suggests you were using an unregulated PSU which had too high a current rating, and/or had the brightness pot set past half-way (against recommended setting). It is unlikely anything else was damaged... it's surprising to me that it happens, but I know of another case of repeated blowing of BC337. Perhaps the design is faulty. Hmm.... Running sammichSID with a PSU such as unregulated 12V AC 500mA (or regulated 12V DC) and brightness set to half-way should prevent it in future. Quote Link to comment Share on other sites More sharing options...
taximan Posted August 27, 2010 Author Report Share Posted August 27, 2010 Hrrrrphhhh......(shuffles feet and looks at floor)......yup the brightness pot was past half way,so that means that either.... A. I missed that bit in the guide or B. I saw that bit and ignored it Anyhow thanks for the input Wilba. cheers Paul Quote Link to comment Share on other sites More sharing options...
Wilba Posted August 27, 2010 Report Share Posted August 27, 2010 Well... page 17 of the 1.0 guide says "Turn brightness pot to approximately 2 o'clock", but the sticker on the LCD says "Set P1 trimpot to half-way (vertical)". A bit inconsistent, eh... However, I've left my sammichSID on overnight at max brightness, using a 12V AC 500mA power supply, and the BC337 didn't blow up. (BTW I don't recommend leaving sammichSID on for hours while unattended). I will have to look into this issue of BC337 possibly exceeding it's limits when unregulated power is too high a voltage. So what power supply are you using? Quote Link to comment Share on other sites More sharing options...
taximan Posted August 27, 2010 Author Report Share Posted August 27, 2010 (edited) Well... page 17 of the 1.0 guide says "Turn brightness pot to approximately 2 o'clock", but the sticker on the LCD says "Set P1 trimpot to half-way (vertical)". A bit inconsistent, eh... However, I've left my sammichSID on overnight at max brightness, using a 12V AC 500mA power supply, and the BC337 didn't blow up. (BTW I don't recommend leaving sammichSID on for hours while unattended). I will have to look into this issue of BC337 possibly exceeding it's limits when unregulated power is too high a voltage. So what power supply are you using? It be diz one..........I just measured it at 14v ac when set on 12v.....could be the problemo? cheers Paul Edited August 27, 2010 by taximan Quote Link to comment Share on other sites More sharing options...
Janis1279 Posted August 27, 2010 Report Share Posted August 27, 2010 Hi , Paul In my Midi Box Cores for LCD drivers I am using 2N2222 and 2N2222A transistors instead of BC337 without any problems. Regards, Janis Quote Link to comment Share on other sites More sharing options...
Wilba Posted August 28, 2010 Report Share Posted August 28, 2010 It be diz one..........I just measured it at 14v ac when set on 12v.....could be the problemo? Maybe. You could probably set this to 9V AC, it might then output ~12V AC under full load. It's a bit hard to test voltage on the pins marked "12V" while the control surface is attached... but do a test without the control surface (or maybe with the LCD removed from the PCB and plugged into the base). Test what voltage you get on the "12V" pins using the 9V AC setting on the PSU... this is with SIDs installed and LCD if you can be bothered... (you'll need to replace the transistor first). If you're getting something over 10.5V DC on the "12V" marked pins (i.e. what will be going into the 7809) then that should be OK. Quote Link to comment Share on other sites More sharing options...
taximan Posted August 31, 2010 Author Report Share Posted August 31, 2010 Hiya, Thanks for the replies and tip about the 2N2222....I have replaced the bc337 and turned down the backlight a smidge and everything is working great now. I do seem to remember noticing the backlight flicker now and again before the bc337 blew,kinda got me thinking that I could have damaged the little bugger when I soldered it in...maybe. Anyhow....onwards and upwards. cheers Paul Quote Link to comment Share on other sites More sharing options...
taximan Posted September 1, 2010 Author Report Share Posted September 1, 2010 Hiya, After reading the post 'sammich problems' I realized that I am using rc37 instead of rc 34. I have searched my emails,the wiki and the forum but can't find it (rc34). Could someone please point me in the right direction? BTW the sammich works okay with the rc37 download but I would rather have the recommended op system. cheers Paul Quote Link to comment Share on other sites More sharing options...
nILS Posted September 1, 2010 Report Share Posted September 1, 2010 I am fairly certain that RC34 was the current and recommended version back when wherever-you-found-this-number was written. The most recent one is the one you want. Going back to outdated versions is bad, fixing possible problems in newer ones is good. Quote Link to comment Share on other sites More sharing options...
Wilba Posted September 2, 2010 Report Share Posted September 2, 2010 The latest version of MIDIbox SID V2 Synth firmware is recommended and will always work with sammichSID. The only difference between "setup_sammich_sid.hex" and the other firmware files is handling the specific control surface, the synth engine is identical. So there will never come a time when you can't upgrade to the latest firmware. Quote Link to comment Share on other sites More sharing options...
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