david winter
Classical music lover.
Hi,
I have almost fully recaped this HK430 except for the four big fat 4700/35. I tested them, they are right in value and have a leak current under 150µA under 25V. Around 200µA/250µA at 30V so I guess they are ok. I also left the two 2200/35 under the chassis as I need to order them.
When I turned the amp on, I kept my finger on the power switch. Under a first test, I had the radio working ok but when passing in AUX I noticed some light static in the left channel. This static ended up in a low 100Hz in the speaker so I immediately switched the amp off to avoid further damage. The output transistors are all ok. While the left channel still works, it has lower gain in FM mode so I need to send a sine wave at both inputs of power board to see where the problem comes from.
After checking this thread I read that some transistors should be replaced in the differencial and current source. I did it several times on other amps (especially with these 2-in-1 transistors).
My question is what is best to replace:
- the three 2CS1345 for the differencial (they have oxided legs): would KSC-1845A be enough ? I read in the linked thread that I need a matched pair with a gain of at least 1000 in the diff and at least 500 in the current source. The recommended replacement is a ZTX694B but since the post is 7 years old this sub could be discontinued already.
- the 2SC458 as well with oxided legs. What best sub for this one ?
Thanks !
David
I have almost fully recaped this HK430 except for the four big fat 4700/35. I tested them, they are right in value and have a leak current under 150µA under 25V. Around 200µA/250µA at 30V so I guess they are ok. I also left the two 2200/35 under the chassis as I need to order them.
When I turned the amp on, I kept my finger on the power switch. Under a first test, I had the radio working ok but when passing in AUX I noticed some light static in the left channel. This static ended up in a low 100Hz in the speaker so I immediately switched the amp off to avoid further damage. The output transistors are all ok. While the left channel still works, it has lower gain in FM mode so I need to send a sine wave at both inputs of power board to see where the problem comes from.
After checking this thread I read that some transistors should be replaced in the differencial and current source. I did it several times on other amps (especially with these 2-in-1 transistors).
My question is what is best to replace:
- the three 2CS1345 for the differencial (they have oxided legs): would KSC-1845A be enough ? I read in the linked thread that I need a matched pair with a gain of at least 1000 in the diff and at least 500 in the current source. The recommended replacement is a ZTX694B but since the post is 7 years old this sub could be discontinued already.
- the 2SC458 as well with oxided legs. What best sub for this one ?
Thanks !
David