Got an amplifier to repair that from nature needs slow transistors in the output to operate properly
Rails are 53+53 DC and there is 4 transistors per amplifier
Problem is that i choose to go with ST TIP 3055 -2955 F to preserve the "'slow "" of the thing while my semis seem to be rated 100v
Anyone thinks that i am playing with fire ?
Kind regards
Sakis
Rails are 53+53 DC and there is 4 transistors per amplifier
Problem is that i choose to go with ST TIP 3055 -2955 F to preserve the "'slow "" of the thing while my semis seem to be rated 100v
Anyone thinks that i am playing with fire ?
Kind regards
Sakis
A bit close to the tolerance voltage limit.
Are they TO220/239 case?
There are lots to choose from dependent on power requirements. Without further detail I cannot comment further.
What do you mean by "Slow" type? That will have little effect on the performance as the amplifier will have compensation in the feed back loop to stop the amplifier from taking off at high frequencies.
Why not replace with the original types?
Are they TO220/239 case?
There are lots to choose from dependent on power requirements. Without further detail I cannot comment further.
What do you mean by "Slow" type? That will have little effect on the performance as the amplifier will have compensation in the feed back loop to stop the amplifier from taking off at high frequencies.
Why not replace with the original types?
case is TO 247
The specific amplifier is unique world wide regarding the output stage ...Analyzing the concept and what the Brit had in mind will raise a big discussion
Originals was factory stamped secret style BD249-250 closed TO247 type plastic
many replaced with 2SB 817 2SD1047 combos and run in to stability problems (15MHZ device )
Kind regards
Sakis
The specific amplifier is unique world wide regarding the output stage ...Analyzing the concept and what the Brit had in mind will raise a big discussion
Originals was factory stamped secret style BD249-250 closed TO247 type plastic
many replaced with 2SB 817 2SD1047 combos and run in to stability problems (15MHZ device )
Kind regards
Sakis
That would explain the failure. 106volts rail to rail and the best version BD pair is maximum C-E 100volts.
The 2SB/D equivalents are more suited voltage wise and can be easily slowed down. Fit a 47pF cap C-B to each output transistor and a 22R Base feed resistor to stop any parasitic oscillation.
Here is a useful link for supplies; 2SD1047 / 2SB817 NPN / PNP Planar Power Transistor Complimentary Pair | eBay
Unless you have an account with Farnel, RS or Mouser etc.
Unless you have an account with Farnel, RS or Mouser etc.
yet again ...
Measures like that already factory exist ( and also responsible for the sonic signature of the specific amplifier )
As about the failure mode i don't think that has much to do with rail voltage versus transistor specs . In the specific amplifier this has only to do with a mechanical construction ERROR that doesn't allow huge heatsinks to work properly and efficiently enough .
Obviously in the design the error exists and the arrogance from the UK manufacturer to allow the machine in the market including a fatal error ...
here is a close up of how wrong trs are mounted while one encapsulated bolt ( as seen in the second picture ) forces the transistor out of the heatsink which is 15cm long and 1.5mm thick to cool 100W amplifier and includes curves which in combination with the bolt make things even worst
... Still in the "frame'' of the case a huge heatsink stands but has no actual contact with the transistors and only with the frame of the case which is the "'real" heatsink
Picture one :close up
Picture two : encapsulated bolt detail
Picture three useless heatsink
Kind regards
Sakis
Measures like that already factory exist ( and also responsible for the sonic signature of the specific amplifier )
As about the failure mode i don't think that has much to do with rail voltage versus transistor specs . In the specific amplifier this has only to do with a mechanical construction ERROR that doesn't allow huge heatsinks to work properly and efficiently enough .
Obviously in the design the error exists and the arrogance from the UK manufacturer to allow the machine in the market including a fatal error ...
here is a close up of how wrong trs are mounted while one encapsulated bolt ( as seen in the second picture ) forces the transistor out of the heatsink which is 15cm long and 1.5mm thick to cool 100W amplifier and includes curves which in combination with the bolt make things even worst
... Still in the "frame'' of the case a huge heatsink stands but has no actual contact with the transistors and only with the frame of the case which is the "'real" heatsink
Picture one :close up
Picture two : encapsulated bolt detail
Picture three useless heatsink
Kind regards
Sakis
no it will not ...screws are as tight is possible but what creates the problem is that the encapsulated bolt is actually "'sitting "" on the curve and that makes it misplaced versus the vertical axis of the "heatsink"
Tightening the screw will force the transistor away from the surface of the heatsink
Tightening the screw will force the transistor away from the surface of the heatsink
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If you ever produced a consumer amplifier you will say that this type of construction and especially with that level of accuracy and even for massive production as seen in the pictures now days and generally will be impossible to produce since costs so much .
means that people had the guts and the money to produce a modern engineering and metalwork miracle but just made a serious design error ...classic British case !!!
Kind UK regards
Sakis
means that people had the guts and the money to produce a modern engineering and metalwork miracle but just made a serious design error ...classic British case !!!
Kind UK regards
Sakis
If you look at the datasheet, you'll see that at 100Vce the allowed current is very, very small, much less than what the Pc would suggest. Keyword here is Safe Operating Area.
So those transistor are very unreliable at the max Vce especially if they need to source some current!
jan
I cannot agree with your last sentence as most of this type of stuff was not made in the UK but sourced in another country and badged over here! The worst in the PA field came from Turkey and Italy. Take the new range of Mackie Powered speakers for instance.
I listen Jan ...will keep this in mind ( I will at the specs once more )
as we speak i am trying to solve the problem with the costumer and explain to him that beyond rail issues there has to be a mechanical improvement to gain some heatsink efficiency . ( while the costumer wants to preserve the amp in original condition in order not to loose second hand value )
Kind regards
Sakis
as we speak i am trying to solve the problem with the costumer and explain to him that beyond rail issues there has to be a mechanical improvement to gain some heatsink efficiency . ( while the costumer wants to preserve the amp in original condition in order not to loose second hand value )
Kind regards
Sakis
4Mhz slow enough for you? (the TIP are 2.5Mhz)
http://www.onsemi.com/pub/Collateral/MJW21193-D.PDF
4A SOA at 50V.
http://www.onsemi.com/pub/Collateral/MJW21193-D.PDF
4A SOA at 50V.
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Sorry John ... this the 1990-2000 we are talking about ...at the time small UK factories produced everything there not much made in China ...
I can post pictures for you with other similar companies made the same arrogant mistakes like Audiolab , Quad , and Cambridge audio did in the past...This is the approach ...The case and engineering is designed and made in UK for this amp ...
Don't think so the area and thickness is too small for 100W amplifier ...
the best way will be to cut totally the bracket that holds the bolts and the transistors , install a thick aluminum of lets say 1 cm thick X15 cm long X5 cm high drilled through ...create drills with screw on the main heatsink and screw sandwich style the transistors to the main heatsink with long screws ...It will last for ever .
the best way will be to cut totally the bracket that holds the bolts and the transistors , install a thick aluminum of lets say 1 cm thick X15 cm long X5 cm high drilled through ...create drills with screw on the main heatsink and screw sandwich style the transistors to the main heatsink with long screws ...It will last for ever .
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