Just make sure you put the new caps in exactly the same polarity as the old ones you take out - sketch up a drawing to be sure. You do not want a cap of that size with reversed voltage applied to it.
This should be the wiring diagram of the PSU in your 400A.
The caps have a different value, but the wiring will be the same. The diode bridge here is rated at 35A at 200V.
Also I think the sec voltage should be more like 55VAC rather than the shown 45VAC - if the rails as shown on the amp schematic are to be approx 75VDC.
The caps have a different value, but the wiring will be the same. The diode bridge here is rated at 35A at 200V.
Also I think the sec voltage should be more like 55VAC rather than the shown 45VAC - if the rails as shown on the amp schematic are to be approx 75VDC.
Gary, in one of my previous posts, I mentioned that I am a newbie when it comes to electronics work.
The 2 PSU capacitors are on the way, but before I would do more than replace the PSU caps on the 400A, I think I should first build one of the ACA amps, like the ACA MinMax, when it becomes available, as it looks to be one of the better ACA options - do you agree?
Anyhow, after building the MinMax, and maybe replacing the 400A PSU caps, I thought I would build another Pass Amp, then maybe do the rest of the upgrade on the 400A. What are your thoughts on that plan?
Regarding the parts for the 400A upgrade, I heard that Jon sells an upgrade kit? Is that correct? What does it usually run?
The 2 PSU capacitors are on the way, but before I would do more than replace the PSU caps on the 400A, I think I should first build one of the ACA amps, like the ACA MinMax, when it becomes available, as it looks to be one of the better ACA options - do you agree?
Anyhow, after building the MinMax, and maybe replacing the 400A PSU caps, I thought I would build another Pass Amp, then maybe do the rest of the upgrade on the 400A. What are your thoughts on that plan?
Regarding the parts for the 400A upgrade, I heard that Jon sells an upgrade kit? Is that correct? What does it usually run?
Yeh, I gathered that was the case, but many members around here probably started out just like you.
Agree on the ACA - any of the ACA options would be good, although limited in power output.
A couple of amp builds under your belt would be advantageous before attempting a full 400A upgrade for sure - but we are here to help. The F5M would be a good option after the ACA.
I am in Australia, and have only had dealings with Jon by email - he was always most helpful and generous with his time and knowledge on the Threshold amps. I would say contact him to see what he can offer with regards an upgrade kit, obviously you would not need the PSU caps.
Fortunately your FE boards look pretty clean and reusable, the rebuilds I have been involved in have all had to have the FE boards replaced with the newer Nelson Pass Stasis FE board ( there is a thread about that you might want to look at) on the forum. This is that thread: https://www.diyaudio.com/community/threads/new-stasis-front-end.363701/
There are a lot of other Threshold threshold rebuild thread in the Passlabs forum, a few on the 400A even - just do a search.
Gary.
Agree on the ACA - any of the ACA options would be good, although limited in power output.
A couple of amp builds under your belt would be advantageous before attempting a full 400A upgrade for sure - but we are here to help. The F5M would be a good option after the ACA.
I am in Australia, and have only had dealings with Jon by email - he was always most helpful and generous with his time and knowledge on the Threshold amps. I would say contact him to see what he can offer with regards an upgrade kit, obviously you would not need the PSU caps.
Fortunately your FE boards look pretty clean and reusable, the rebuilds I have been involved in have all had to have the FE boards replaced with the newer Nelson Pass Stasis FE board ( there is a thread about that you might want to look at) on the forum. This is that thread: https://www.diyaudio.com/community/threads/new-stasis-front-end.363701/
There are a lot of other Threshold threshold rebuild thread in the Passlabs forum, a few on the 400A even - just do a search.
Gary.
Last edited:
Yeh, I am a retired elect engineer, having worked in heavy power projects - AC and DC variable speed drives etc. But I have built amps all my life since leaving school, starting off with tube amps, then on to solid state with the odd tube amp thrown in over time.
Wow, what a skillset! After graduating from high school I tried to become an electronics engineer. I attended a technical school at a technical college. Early on, I realized that it didn't seem to be something that I wanted to do, so I dropped out.
What stereo equipment do have now? What kind of speakers?
What stereo equipment do have now? What kind of speakers?
The links that you gave me for upgrading a stasis amp. Would that be a better option for my 400A?
If your current FE boards are working, then I would stay with them - from your pics, they look quite clean actually. The other rebuilds I have been involved in had damaged/burnt original FE boards with blown components, and we replaced those with the new Pass FE boards (Zen Mod has also done a pcb of the same design but on a smaller sized pcb). They all worked out well with happy owners.
Currently I am using a Nelson Pass FE2022 as a preamp driving the Zen Mod Babelfish F8 power amp into a mint pair of old Yamaha NS1000M speakers. I use either a Sony NW-ZX300 digital audio player or an Advance Acoustic MCD-204 tube output CD player as a source. I can alternate at times with a couple of different tube preamps, and other power amps as I might build them. I am currently building a Threshold Stasis design at the moment from scratch, using the NP FE boards and Zen Mods output stage pcb's. It will be a lower power version at about 60wpc class A, totally dual mono with a total of 544,000uF in the PSU - overkill, but I had the caps here waiting to be put to good use.
8 off Nippon Chemi Con made in Japan 68,000uF 50V 105C- only about 6 years old and I got them for a song!!
That is no problem, as most around here have bought their own parts and done the upgrade themselves - with help from other members along the way.