dudewheresmybass Posted January 25, 2022 Share Posted January 25, 2022 Evening chaps. recently my bh250 amp head blew. I have a particularly gifted friend that has spotted a short causes by a loose bolt rattling around inside. min order to fix it, he needs a schematic to identify the resistor’s value that has blown. Does anyone have one or know where I can find one. My Google searches have shown up nothing so far. thanks in advance 👍👍 Quote Link to comment Share on other sites More sharing options...
gary mac Posted January 27, 2022 Share Posted January 27, 2022 When trying to repair a BH250 for a customer, I could get no help, schematics or advice from them. They have an approved repairer in Sheffield (name escapes me at the moment). What with courier fees, each way and a minimum charge to look at it, it wasn't cost effective to get it fixed. Quote Link to comment Share on other sites More sharing options...
BassBunny Posted January 27, 2022 Share Posted January 27, 2022 3 hours ago, gary mac said: When trying to repair a BH250 for a customer, I could get no help, schematics or advice from them. They have an approved repairer in Sheffield (name escapes me at the moment). What with courier fees, each way and a minimum charge to look at it, it wasn't cost effective to get it fixed. That'll be Real Electronics. They are also the authorized repair agents for Mark Bass and there's quite a bit on here about them. £35 to diagnose the problem, which you get back if you go ahead. £69 fixed labour, £18 courier fee to send it back + parts + VAT on the total amount. I am pretty sure they don't repair to component level. They are just "board swappers". Quote Link to comment Share on other sites More sharing options...
dudewheresmybass Posted January 28, 2022 Author Share Posted January 28, 2022 21 hours ago, gary mac said: When trying to repair a BH250 for a customer, I could get no help, schematics or advice from them. They have an approved repairer in Sheffield (name escapes me at the moment). What with courier fees, each way and a minimum charge to look at it, it wasn't cost effective to get it fixed. All I’m looking for is a value of a resistor. It shouldn’t really be that hard! Lol Its R140. everything else works fine, but this will restore it to a completely working condition. 👍 Quote Link to comment Share on other sites More sharing options...
gary mac Posted January 28, 2022 Share Posted January 28, 2022 Good luck with it, hope you can get sorted. Quote Link to comment Share on other sites More sharing options...
dudewheresmybass Posted January 28, 2022 Author Share Posted January 28, 2022 Cheers 👍👍 Quote Link to comment Share on other sites More sharing options...
yorks5stringer Posted January 30, 2022 Share Posted January 30, 2022 There's a guy on YouTube who may be able to help, called bigclivedotcom. He uses some sort of database to find out the values of caps and resistors...... 2 Quote Link to comment Share on other sites More sharing options...
basstone Posted January 31, 2022 Share Posted January 31, 2022 On 28/01/2022 at 11:55, dudewheresmybass said: All I’m looking for is a value of a resistor. It shouldn’t really be that hard! Lol Its R140. everything else works fine, but this will restore it to a completely working condition. 👍 Can you be sure that this is the only faulty component? Has everything else been tested at component level? Unless the circuit and the failure mode is known there may be other issues lurking in there as well. Of course you may be correct and just a resistor is needed and it's certainly worth a trying a replacement if you can find out what the value is. The only other suggestion that I can offer is that someone else who has the same amp could take a photo of the circuit board to identify the value of the resistor in question. Anyway good luck with it. 1 Quote Link to comment Share on other sites More sharing options...
dudewheresmybass Posted January 31, 2022 Author Share Posted January 31, 2022 Everything else is in working order. it’s all been tested and this is the problem. a pic of the board would be an ideal solution. 👍👍 1 Quote Link to comment Share on other sites More sharing options...
basstone Posted January 31, 2022 Share Posted January 31, 2022 6 minutes ago, dudewheresmybass said: Everything else is in working order. it’s all been tested and this is the problem. a pic of the board would be an ideal solution. 👍👍 Hopefully if the thread is kept active someone will spot it and offer to take a photo. If you can't get a photo, another, not so easy option, is to trace that part of the circuit out and figure out what the component does. Depending on accessibility and the board construction this could be tricky and time consuming! The only 2 variables are its resistance and power rating. There is hopefully some clue of power rating at least based on the size / lead spacing of the old component. Depending on its function, the exact value may not be that critical. 1 Quote Link to comment Share on other sites More sharing options...
dudewheresmybass Posted January 31, 2022 Author Share Posted January 31, 2022 My friend says it's functioning as part of a potential divider where the positive DC power comes into the amp board from the power supply board. May as well be japanese to me 🤷♂️ Quote Link to comment Share on other sites More sharing options...
BassBunny Posted January 31, 2022 Share Posted January 31, 2022 18 minutes ago, dudewheresmybass said: My friend says it's functioning as part of a potential divider where the positive DC power comes into the amp board from the power supply board. May as well be japanese to me 🤷♂️ Can you not identify the value from the coding rings in the resistor or is it completely fried? Failing that if it's got to be removed anyway, quite often component values are printed on the PCB where they live. Might be worth a look. 1 Quote Link to comment Share on other sites More sharing options...
dudewheresmybass Posted January 31, 2022 Author Share Posted January 31, 2022 There aren't any markings on the board unfortunately - except the marking R140, and the component was truly fried lol A loose nut had arc'ed it out to one of the columns supporting a different board Quote Link to comment Share on other sites More sharing options...
dudewheresmybass Posted January 31, 2022 Author Share Posted January 31, 2022 Quote Link to comment Share on other sites More sharing options...
basstone Posted January 31, 2022 Share Posted January 31, 2022 1 minute ago, dudewheresmybass said: Looks like R140 and R141 are both missing. Both small SMD items so not much power dissipation I think? Those solder pads also look damaged. It looks like the short was to the pillar on the left judging by the melted bit and black soot? Quote Link to comment Share on other sites More sharing options...
dudewheresmybass Posted February 1, 2022 Author Share Posted February 1, 2022 18 hours ago, basstone said: Looks like R140 and R141 are both missing. Both small SMD items so not much power dissipation I think? Those solder pads also look damaged. It looks like the short was to the pillar on the left judging by the melted bit and black soot? from what I've been told, 141 is on the underside. The picture before was quite some crime scene lol (I dont't have it unfortunately), but the pillar is definitely the culprit Quote Link to comment Share on other sites More sharing options...
bnt Posted February 5, 2022 Share Posted February 5, 2022 Personally, if all else failed, I’d be willing to experiment a bit in an attempt to save the amp. It’s a tiny SMD resistor that had quite a voltage going to it, so I’d start with a high value such as 1M. Using a pot to dial in a value might be an option too, in series with e.g. a 1k to limit the possible current. 1 Quote Link to comment Share on other sites More sharing options...
2x18 Posted February 5, 2022 Share Posted February 5, 2022 Photo of mine --hope it helps Will. 1 1 Quote Link to comment Share on other sites More sharing options...
basstone Posted February 6, 2022 Share Posted February 6, 2022 17 hours ago, 2x18 said: Photo of mine --hope it helps Will. R140 looks like 350 ohms from this photo and R141 as already noted on the other side of the board. Worth trying a temporary "breadboard" fix with a standard resistor to see if it all springs back to life? 1 Quote Link to comment Share on other sites More sharing options...
Bigguy2017 Posted February 6, 2022 Share Posted February 6, 2022 No, it's 35R - the SMD resistor code is XXY where XX is value and Y is number of zeroes added i.e. 35 and zero zeroes = 35R 2 Quote Link to comment Share on other sites More sharing options...
dudewheresmybass Posted February 8, 2022 Author Share Posted February 8, 2022 I passed the pic along to my 'chap' lol Apparently he tells me that its actually supposed to read 35c, which is a resistance of 22.6 ohms. Either way, he says a massive Thank you to those that have helped. 👍 Hopefully I should have a working amp again soon! 🤞🤞🤘 Quote Link to comment Share on other sites More sharing options...
basstone Posted February 8, 2022 Share Posted February 8, 2022 12 minutes ago, dudewheresmybass said: I passed the pic along to my 'chap' lol Apparently he tells me that its actually supposed to read 35c, which is a resistance of 22.6 ohms. Either way, he says a massive Thank you to those that have helped. 👍 Hopefully I should have a working amp again soon! 🤞🤞🤘 You live and learn! I don't get involved with much SMT but a short google search came up with the EIA-96 codes which would indicate that 35C is 226 X 100 or 22.6Kohms as 35 is code for 226 and C is a x100 multiplier. All potentially quite confusing and ambiguous if the markings become worn! Fingers crossed for the repair 1 1 Quote Link to comment Share on other sites More sharing options...
Bigguy2017 Posted February 8, 2022 Share Posted February 8, 2022 3 hours ago, dudewheresmybass said: I passed the pic along to my 'chap' lol Apparently he tells me that its actually supposed to read 35c, which is a resistance of 22.6 ohms. Either way, he says a massive Thank you to those that have helped. 👍 Hopefully I should have a working amp again soon! 🤞🤞🤘 My old eyes aren't what they used to be..... 😞 1 Quote Link to comment Share on other sites More sharing options...
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