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Tc electronic bh250 woes.


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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 👍👍

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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.

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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".

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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. 👍

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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.

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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.

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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.

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1 minute ago, dudewheresmybass said:

bh250 circuit.JPG

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?

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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 

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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. 

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17 hours ago, 2x18 said:

Photo of mine --hope it helps

 

Will.IMG_0481.thumb.jpeg.dfd03bea22c5fbf50d47a147822b38df.jpeg

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?

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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

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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..... 😞

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