elza
Active Member
I decided to replace the filter caps in my PL400. I was vacillating as to whether to change the control board. When I opened it up I discovered one of the electrolytics on the control board to be swollen. (Shown in picture pl4) Having read so much about the White Oak board I decided to go for it.
Pictures are available at this URL: http://schroeder-family.us/temp2/
The filter change was fairly straight forward. I opted for the 16,800 uf version. While it is supposed to be a drop-in replacement it takes a bit of work to fit it in. It fits but just barely and the transformer wires are a bit short. But with a minimum of fuss they went into place. I’ve heard it recommended that a heavier bridge rectifier be installed. The original is 25 amp so 35 sounded like a reasonable increase. All that was available at the local electronics shop was a 40 amp. Better too much than too little.
The control board was a different story. I decided to go with the kit as opposed to the assembled version. I spent 8 or 9 hours assembling it. It really isn’t worth the difference in cost versus the hours involved unless you just like to do things like this. I do so I rather enjoyed the time spent. However, this is not a job for a novice. You will need a very well developed soldering technique and a good quality soldering station. The board is small and heavily populated. The component count ran 178 if I counted correctly. This results in small, closely spaced pads that are easily damaged or bridged. My iron is equipped with a 1/64” tip and I still managed to bridge one solder joint.
The kit is one of the best I’ve seen. A great deal of thought and effort went into it. Each group of components is in a separate bag with the value and location printed on it. Resistors even have the color code on the label. Each bag is accounted for on an Excel spread sheet again with values and location printed on the list. There is a column to check off each bag as it is used. It is arranged in the order of size starting with the components mounted closest to the board. The quality of the parts and board is second to none. The documentation is thorough and complete. VERY thorough and complete.
Once the board was completed installation was a snap. On the original board (mine was the 14B version) the +Vcc was attached to the right channel side. On the White Oaks it attached to the left channel side. Otherwise it is a wire-for-wire change out.
Following the installation I powered it up with a DBT. Everything appeared good and the voltages looked OK. I set the bias and let it cook. Since no smoke appeared I ran it up on full voltage and let it warm up for a while. All voltages looked good. The bias has plenty of range and was easily set to 380 mV. Offset is 12mV and 15mV left and right respectively. Time to plug it into the system and give it a listen.
If I had not done this myself I wouldn’t believe it was the same amplifier! The sound is truly incredible. The clarity is better by several orders of magnitude. The mids are clean and crisp and the bass is out of this world. With a punchy bass line it feels like someone if thumping you in the chest. You can literally feel the bass now. I really didn’t realize how muddy and sluggish it was before.
My suggestion is if you haven’t upgraded yet DO IT!! Now! You will truly fall in love with the improved sound quality. And the stuff from White Oak is outstanding.
Next comes the protection relay for the 400 followed by re-caping the x-overs and the Spec-1. Busy hands are happy hands.
Pictures are available at this URL: http://schroeder-family.us/temp2/
The filter change was fairly straight forward. I opted for the 16,800 uf version. While it is supposed to be a drop-in replacement it takes a bit of work to fit it in. It fits but just barely and the transformer wires are a bit short. But with a minimum of fuss they went into place. I’ve heard it recommended that a heavier bridge rectifier be installed. The original is 25 amp so 35 sounded like a reasonable increase. All that was available at the local electronics shop was a 40 amp. Better too much than too little.
The control board was a different story. I decided to go with the kit as opposed to the assembled version. I spent 8 or 9 hours assembling it. It really isn’t worth the difference in cost versus the hours involved unless you just like to do things like this. I do so I rather enjoyed the time spent. However, this is not a job for a novice. You will need a very well developed soldering technique and a good quality soldering station. The board is small and heavily populated. The component count ran 178 if I counted correctly. This results in small, closely spaced pads that are easily damaged or bridged. My iron is equipped with a 1/64” tip and I still managed to bridge one solder joint.
The kit is one of the best I’ve seen. A great deal of thought and effort went into it. Each group of components is in a separate bag with the value and location printed on it. Resistors even have the color code on the label. Each bag is accounted for on an Excel spread sheet again with values and location printed on the list. There is a column to check off each bag as it is used. It is arranged in the order of size starting with the components mounted closest to the board. The quality of the parts and board is second to none. The documentation is thorough and complete. VERY thorough and complete.
Once the board was completed installation was a snap. On the original board (mine was the 14B version) the +Vcc was attached to the right channel side. On the White Oaks it attached to the left channel side. Otherwise it is a wire-for-wire change out.
Following the installation I powered it up with a DBT. Everything appeared good and the voltages looked OK. I set the bias and let it cook. Since no smoke appeared I ran it up on full voltage and let it warm up for a while. All voltages looked good. The bias has plenty of range and was easily set to 380 mV. Offset is 12mV and 15mV left and right respectively. Time to plug it into the system and give it a listen.
If I had not done this myself I wouldn’t believe it was the same amplifier! The sound is truly incredible. The clarity is better by several orders of magnitude. The mids are clean and crisp and the bass is out of this world. With a punchy bass line it feels like someone if thumping you in the chest. You can literally feel the bass now. I really didn’t realize how muddy and sluggish it was before.
My suggestion is if you haven’t upgraded yet DO IT!! Now! You will truly fall in love with the improved sound quality. And the stuff from White Oak is outstanding.
Next comes the protection relay for the 400 followed by re-caping the x-overs and the Spec-1. Busy hands are happy hands.
