Hi
I have two of these amps
The output devices are 2sj82/3 and 2sk226/7 if two hole fixing.
These are difficult to replace with alternatives without extensive circuit changes due to circuit stability. From memory the other transistors are mpsa general transistors. You can probably change for bc 550/560.
If the amplifier is the Dr T or the Studio T the circuit is probably the same as the Dr T. I have a schematic that I drew at home. If the amplifier is called the DR T Mk 2 it may have the same circuit as the P270. That circuit is on diyaudio.
I would check the output devices before assuming that they are damaged. This is a cool running amplifier with low bias and damage to output devices is not usual.
The usual fault is that resistors on the power supply rails burn out. They reduce the voltage from 62v to 18v for the input stage. From memory they are 1500ohm 3 watt. I change them to 20 watt but they still run hot. Later models changed these to a pass transistor arrangement.
The power supply is basic with only 22,000uf per rail feeding two 150 watt channels. The transformer is 625va with 62 0 62 vdc rails. It benefits from a bridge per channel and additional capacitance.
Don
I have two of these amps
The output devices are 2sj82/3 and 2sk226/7 if two hole fixing.
These are difficult to replace with alternatives without extensive circuit changes due to circuit stability. From memory the other transistors are mpsa general transistors. You can probably change for bc 550/560.
If the amplifier is the Dr T or the Studio T the circuit is probably the same as the Dr T. I have a schematic that I drew at home. If the amplifier is called the DR T Mk 2 it may have the same circuit as the P270. That circuit is on diyaudio.
I would check the output devices before assuming that they are damaged. This is a cool running amplifier with low bias and damage to output devices is not usual.
The usual fault is that resistors on the power supply rails burn out. They reduce the voltage from 62v to 18v for the input stage. From memory they are 1500ohm 3 watt. I change them to 20 watt but they still run hot. Later models changed these to a pass transistor arrangement.
The power supply is basic with only 22,000uf per rail feeding two 150 watt channels. The transformer is 625va with 62 0 62 vdc rails. It benefits from a bridge per channel and additional capacitance.
Don
This one was really a Greek gift
I remember one of the most famous Greek gifts was the Trojan horse...filled with warriors.
This one is filled with rust...will be a hard work.
In my country we have a say...referenced in the Trojan Horse...
- " this is a Greek gift! "
Means a not so good gift...hehe
Good that we have a Greek friend in our forum.
Image is from dear Sakis with a Spartan Helmet
regards,
Carlos
I remember one of the most famous Greek gifts was the Trojan horse...filled with warriors.
This one is filled with rust...will be a hard work.
In my country we have a say...referenced in the Trojan Horse...
- " this is a Greek gift! "
Means a not so good gift...hehe
Good that we have a Greek friend in our forum.
Image is from dear Sakis with a Spartan Helmet
regards,
Carlos
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