Pioneer SA-7800 Recap Question

[Pubcha]

I just picked up a Pioneer SA-7800 to restore as a summer project. The phono section is having some issues. But, I am learning that this seems to be a common issue and I am lucky there is a lot of information out there to help guide me when fixing this.

The main reason for my post is a question about the different Nichicon capacitor series. To give you some background, my first recap project was a Yamaha CA-610 while in COVID isolation 2 years back. I made many mistakes in that project but learned a lot in the process. When recapping the Yamaha, I decided to go with the highest-level Nichicon audio caps (UKZ, UFG) in every location. I understand the error of my ways now and feel a bit silly installing these in the areas such as the VU meter circuit.

From a couple days of reading about the SA-7800, I have gained a high respect for markthefixer. I have seen some of his recap lists for the power supply and power amplifier assembly, which recommend low leakage (UKL)/low impedance (UPW) caps. After seeing these lists, I just assumed I would use the audio-grade UKZ/UFG caps in the phono circuit. However, I just came across a post from markthefixer recommending low impedance (UPW) caps in this circuit, and I was surprised.

My main question here is what are the benefits in using the low impedance series of caps in this circuit over the audio-grade UKZ/UFGs? And, if the best choice is the low impedance caps, when is it appropriate to use the audio-grade caps? I am asking this question to learn from the experts here on the board who are familiar with the SA-7800. I do know there are many forums that go on for pages regarding the choice of capacitor, but I was hoping there was a simple answer for this specific situation.

Thanks!

 

[Krešo]

Hi!

I don't know how much you know on this subject but you are on the right place. My first advise is take it to a pro if you don't know electronics or if you're not sure about it! ;-)

Now, if you go ahead and do this then you should wait for someone with extensive knowledge to chime in. I am a hobbyist and also learning here. And all over the place. But, from my limited knowledge on the subject I can tell you this. Not all Caps are the same nor they behave the same in the circuit. If you know how to read schematics and follow the audio path (each board, from IN to OUT) these will be your "audio grade" Caps. In audio path you can change your suspects with either electrolytics or film. The rest of the circuit is more for "voltage" related so in those places you can go for regular Caps or, as Mouser as just one of may sources, names them "general purpose" Caps. Now, where and when to choose low impedance, low leakage or any other sub-type, it also depends on frequency relation, voltage relation... So, as you can see, Caps are field on it's own and really needs proper knowledge and attention. I advise you to browse AK and I am almost sure that someone here has done full restoration on SA-7800 so you can find newly made BOM. Or any other Pioneer of similar range and use that as your base for study. I am sure you will see how there have been used 3 types of Caps at the most. Then study where are those in the circuit and read their spec. sheets a bit. Soon you'll get the picture. I am sorry for not being able to help out in specifics but wait a bit and some more knowledgeable than me will get back to you. I have learned a lot here. A lot! But it takes time. And I have just scratch the surface.

Sidenote: compare those suffixes/prefixes and try finding your values on Moser or Digikey. Check where in the circuit

 

[Pubcha]

Hi!

I don't know how much you know on this subject but you are on the right place. My first advise is take it to a pro if you don't know electronics or if you're not sure about it! ;-)

Now, if you go ahead and do this then you should wait for someone with extensive knowledge to chime in. I am a hobbyist and also learning here. And all over the place. But, from my limited knowledge on the subject I can tell you this. Not all Caps are the same nor they behave the same in the circuit. If you know how to read schematics and follow the audio path (each board, from IN to OUT) these will be your "audio grade" Caps. In audio path you can change your suspects with either electrolytics or film. The rest of the circuit is more for "voltage" related so in those places you can go for regular Caps or, as Mouser as just one of may sources, names them "general purpose" Caps. Now, where and when to choose low impedance, low leakage or any other sub-type, it also depends on frequency relation, voltage relation... So, as you can see, Caps are field on it's own and really needs proper knowledge and attention. I advise you to browse AK and I am almost sure that someone here has done full restoration on SA-7800 so you can find newly made BOM. Or any other Pioneer of similar range and use that as your base for study. I am sure you will see how there have been used 3 types of Caps at the most. Then study where are those in the circuit and read their spec. sheets a bit. Soon you'll get the picture. I am sorry for not being able to help out in specifics but wait a bit and some more knowledgeable than me will get back to you. I have learned a lot here. A lot! But it takes time. And I have just scratch the surface.

Sidenote: compare those suffixes/prefixes and try finding your values on Moser or Digikey. Check where in the circuit

Thanks so much for your help!

 

[Krešo]

Here, check this out. Taken from Nichicon web. This helped me out. Read carefully each group and sub-group and you'll quickly figure out what each suffix/prefix means and where in the circuit it should go. Some of the memebers here with long and extensive experience know this by hard. The rest of us learn. ;-)