If you want to improve your amplifier, I believe that the first filter capacitor must be replaced anyway because 150uF is twice the maximum allowed value for the rectifier tube. I've often seen this design mistake on low end China tube amplifier, they do this maybe because 150uF is a common/cheaper value, or because they account for a fast degradation of the capacitor due to poor quality. If your amplifier is 6+ month old, the rectifier tube may already starting to wear out due to the overload.
@bloo - threads merged. Please do NOT start multiple threads for the same project or topic.First of all, the two 150uf caps are not connected together, there is a choke between their positive terminals. The two negative terminals are connected but not the positive.
Please read my previous posts again.
As I pointed out, the stock rectifier is being run at or perhaps over its maximum current. In addition, the data sheet for that rectifier says the maximum value for the first cap is only 4 uf.
Step 1: Replace the rectifier with a 5AR4 / GZ34. This can easily handle the current. I would stay away from the Chinese versions.
Step 2: Replace the first cap, which is now 150uf, with a 47uf 450v cap.
Don't waste your money on overpriced boutique caps, especially in the power supply. Just use a quality brand such as Nichicon, Panasonic, Cornell-Dublier, or similar. Get a cap rated for 105 degrees and 10,000 hours and buy it from a major distributor, not on eBay where the possibility of counterfeit parts is higher.
I usually buy from Digi-Key but they are in the U.S. I'm sure there are similar major suppliers of electronic parts in Europe. If you buy from a boutique parts dealer you will end up paying several times more than you need to. Digi-Key lists several of the 47uf caps with the specs I suggested at between $2 and $3 each.
If you want to replace the second 150uf cap, you could go up in value to 270uf, as pcan suggested, or stay with 150uf. Use the same 105 degree 10,000 hour caps I mentioned. If you go with a higher value, check the dimensions and make sure it will physically fit in the amp since it will be larger than a 150uf cap.
Step 3: Measure the voltages in the amp. They may still be too high, depending on how high your wall voltage is. If it is too high it's easy to bring it down but you need to know the voltages first.
After you take these 3 steps, spend some time listening to the amp with the Klipsch speakers.
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You're correct that the 150uf cap is too large but it's not twice the maximum, it's 37.5 times the maximum!
Image resolution is low and I cannot check the wiring properly. On this "old style" forum is best to upload the image directly on the web site, check the guide.
The capacitor to be lowered in value is the one with the positive terminal connected to the rectifier tube socket pin (the socket is at the center). By the way, the capacitors on this picture still have the brand name BC components instead of Vishay, they are very old.
The capacitor to be lowered in value is the one with the positive terminal connected to the rectifier tube socket pin (the socket is at the center). By the way, the capacitors on this picture still have the brand name BC components instead of Vishay, they are very old.
A safety note first. You need to drain the voltage before you touch anything in there. Caps can hold voltage even though the amp is turned off. Do a search and read. It's always best to measure to make sure.
The two red wires in the pic are connected to pin 8 of the rectifier socket. One wire goes to the first cap. That's the cap that should be replaced with the new 47uf 450v part.
The other red wire goes to the choke. The choke will have two wires coming out of it. One connects to the + of the first cap. Going directly to Pin 8 is functionally the same thing since the + of the first cap is connected to that point too. The other choke wire connects to the + of the second cap, which is the other 150uf.
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That probably explains why they use them.
The manufacturer likely bought truckloads of them at a very cheap price because they were so old. Who knows when they were manufactured. The seller probably only had caps in certain values and the manufacturer just uses them even though they are not correct for the application.
The electolyte inside caps can dry up or change in some way even if the cap has never been used. That's why it's risky to buy NOS electrolytic caps.
I would definitely replace both of them with fresh, high quality, caps as suggested earlier.
Yes, it looks like it's probably the one on the right but you need to double check once you're in there.
It also looks like the schematic may not be totally accurate.
The pics show two resistors connected to the + of the second cap and then each one goes to a 22uf cap. The schematic only shows one of these RC sections but apparently there are two - separate supplies to each of the input tubes.
When you order new caps you might just as well order some replacements for the brown caps too. Keep the value at 22uf 450v and get the 105 degree 10,000 hour ones.
The image at post # 48 shows the modern Vishay branded capacitors, rather than the BC components on the previous post n. 46; all capacitors are actually different. It is a good idea to replace them with new ones from a trusted source anyway, the manufacturer clearly uses whatever component he has at hand at the moment.
Hi guys,
I have had one of these amps for a couple weeks now and am trying to track down an issue where the left channel is around 3db louder than the right.
I'm working with Douk who asked me to make a few voltage measurements, which I did and am waiting to hear back from them.
My question, it seems like the caps in question mentioned earlier in this thread are different than the current build, can someone confirm what they've done?
I have had one of these amps for a couple weeks now and am trying to track down an issue where the left channel is around 3db louder than the right.
I'm working with Douk who asked me to make a few voltage measurements, which I did and am waiting to hear back from them.
My question, it seems like the caps in question mentioned earlier in this thread are different than the current build, can someone confirm what they've done?
Yep, swapped tubes left to right and even tried a set of matched 6SN7GTBs
TubeDepot.com | Tung-Sol 6SN7GTB New Prod. Preamp Vacuum Tube
Swapped input and speakers left <-> right, no difference.
So it's those 2 big blue Vishay 150uf caps that should be 47uf, yes?
(not that it's related to my level difference issue, just curious).
TubeDepot.com | Tung-Sol 6SN7GTB New Prod. Preamp Vacuum Tube
Swapped input and speakers left <-> right, no difference.
So it's those 2 big blue Vishay 150uf caps that should be 47uf, yes?
(not that it's related to my level difference issue, just curious).
Don't know, haven't looked at the schem. I would also suspect the vol. pot as well for channel imbalance.
jeff
jeff