Hello,
I am looking for little help with REL Britannia B3 sub amp troubleshooting.
My skill level: electronics engineering background - however have not worked in industry for 20 years or so - so I am I guess less than novice.
Symptoms: - hum with static static "pops", regardless of inputs (or lack off).
Initial diagnosis (my own - very likely wrong): considering subwoofer is 15 yo, very likely PS or amp section caps.
However, upon opening the unit I found the following:
1. Capacitors do not really show signs of "leak" or top lid buldge. (see last two pictures below)
2. I found the signs of component overheating on the - if I understand it correctly - the Power Supply board. (circled in red in first picture). The board on the other side - almost directly under the resistor (is it 1.2k or 12k?) is slightly darkened.
3. I think it is a mosfet - however I would appreciate any suggestion in identification it says DH S48:
3. The caps appear to be in good shape - however I will change them. Only few I can easily source in that range are "snap in" (Nichicon KG or ELNA), the solder one is Mundorf - are they any good?
So, besides questions above - what should I replace first - capacitors or the mosfet? or both?
Can someone confirm what that mosfet is ( or transistor)?
Should I change the resistor in pictures - is it 2 watts one?
I appreciate all help I can get.
Bez
I am looking for little help with REL Britannia B3 sub amp troubleshooting.
My skill level: electronics engineering background - however have not worked in industry for 20 years or so - so I am I guess less than novice.
Symptoms: - hum with static static "pops", regardless of inputs (or lack off).
Initial diagnosis (my own - very likely wrong): considering subwoofer is 15 yo, very likely PS or amp section caps.
However, upon opening the unit I found the following:
1. Capacitors do not really show signs of "leak" or top lid buldge. (see last two pictures below)
2. I found the signs of component overheating on the - if I understand it correctly - the Power Supply board. (circled in red in first picture). The board on the other side - almost directly under the resistor (is it 1.2k or 12k?) is slightly darkened.
3. I think it is a mosfet - however I would appreciate any suggestion in identification it says DH S48:
3. The caps appear to be in good shape - however I will change them. Only few I can easily source in that range are "snap in" (Nichicon KG or ELNA), the solder one is Mundorf - are they any good?
So, besides questions above - what should I replace first - capacitors or the mosfet? or both?
Can someone confirm what that mosfet is ( or transistor)?
Should I change the resistor in pictures - is it 2 watts one?
I appreciate all help I can get.
Bez
I've drawn a blank with the transistor I'm afraid 🙁
As to the resistor, that is a metal oxide type and discolouration is normal when they run very hot. If it reads the correct value out of circuit then its fine, no need to replace. And yes, it looks like a 2 watt type.
I suspect changing parts in hope probably isn't going to fix this, you really need to see a proper circuit diagram to fault find on this.
As to the resistor, that is a metal oxide type and discolouration is normal when they run very hot. If it reads the correct value out of circuit then its fine, no need to replace. And yes, it looks like a 2 watt type.
I suspect changing parts in hope probably isn't going to fix this, you really need to see a proper circuit diagram to fault find on this.
Finding myself in a similar situation but have not been able to find a proper schematic nor fix my amp yet. You should look for lateral mosfet diagrams from Hitachi notes or so for some hints..
An interesting thread is around with useful staff
Anyone here own a Rel Sorm III sub?
An interesting thread is around with useful staff
Anyone here own a Rel Sorm III sub?
Thank you for suggestions. The thread about the Rel Storm is actually exactly what I am experiencing. It appears that actually the resistor seems to be the issue causing the hum and crackling. I will replace it (and capacitors) first and go on from there. Interestingly it shows exactly what I suspect are the components in question:
"Change Q9 & Q10 (BF469, NPN) to MJE340
Change Q4 & Q5 (BF470, PNP) to MJE350
Change R8 (12k, 2 Watt) to 15K, 3 Watt, 5%
Change R6 (10k, 1/8 Watt?) to 22K, 1%"
I am hoping however that mosfets are not faulty and resistor is the only issue. Still if anybody can suggest exactly what these are or what the replacements are I would really appreciate it.
Any thoughts on heat sinkable resistors (usually ones with metal bodies that can be attached to the hit sink) or it had to be "audio" quality (just don't want to start any wars 🙂 )?
Thanks,
Bez.
"Change Q9 & Q10 (BF469, NPN) to MJE340
Change Q4 & Q5 (BF470, PNP) to MJE350
Change R8 (12k, 2 Watt) to 15K, 3 Watt, 5%
Change R6 (10k, 1/8 Watt?) to 22K, 1%"
I am hoping however that mosfets are not faulty and resistor is the only issue. Still if anybody can suggest exactly what these are or what the replacements are I would really appreciate it.
Any thoughts on heat sinkable resistors (usually ones with metal bodies that can be attached to the hit sink) or it had to be "audio" quality (just don't want to start any wars 🙂 )?
Thanks,
Bez.
Your "MOSFET" is a 40V, 2A high-gain, low Vce,sat PNP (PBSS5240X).
Discoloration of solder joints can also be caused by aged flux, if heat is the reason the green solder mask will be brown too.
I would not start changing random parts, especially not without a schematic and not if resistor values are doubled and HF transistors are replaced with types that do not even give the capacitance in the datasheet. Replacing with higher wattage is OK though if the resistor has been running hot. No need for chassis mounting, there is lots of space in that picture even for an axial 5-Watt.
Have not read all of the other thread though, maybe there IS a proven solution. Still, a multimeter can save a lot of solder.
Discoloration of solder joints can also be caused by aged flux, if heat is the reason the green solder mask will be brown too.
I would not start changing random parts, especially not without a schematic and not if resistor values are doubled and HF transistors are replaced with types that do not even give the capacitance in the datasheet. Replacing with higher wattage is OK though if the resistor has been running hot. No need for chassis mounting, there is lots of space in that picture even for an axial 5-Watt.
Have not read all of the other thread though, maybe there IS a proven solution. Still, a multimeter can save a lot of solder.
Thank you very much Holmer!. That helped quite a bit. I agree that diagram would be the best, but as you probably guessed, REL diagrams are hard to find.
Is there a place that I could look these up myself? Or if not - there is also another set of two Q9 and Q10 that read "DD-S40". Would you be kind to decipher these? And I hope it is not too much to ask for: Is there equivalent in different package (ie: To-220) that I could attach heat sink to?
Finally these "upgrades" I got from other post:
"Change Q9 & Q10 (BF469, NPN) to MJE340
Change Q4 & Q5 (BF470, PNP) to MJE350"
Are they indeed upgrades requiring adjustments to the R6 and R8 or the MJEs would work replacing my "mosfets" 🙂 .
Is there a place that I could look these up myself? Or if not - there is also another set of two Q9 and Q10 that read "DD-S40". Would you be kind to decipher these? And I hope it is not too much to ask for: Is there equivalent in different package (ie: To-220) that I could attach heat sink to?
Finally these "upgrades" I got from other post:
"Change Q9 & Q10 (BF469, NPN) to MJE340
Change Q4 & Q5 (BF470, PNP) to MJE350"
Are they indeed upgrades requiring adjustments to the R6 and R8 or the MJEs would work replacing my "mosfets" 🙂 .