Looking to recap my old R2R

[briank]

I guess I don't need to I am just recapping the one side (for now) so I was going to try and keep it the same as the other one. Or am I over thinking it? I have no problem upping to 220 if I can find the right caps.

Theoretically, I'd expect the act of re-capping alone to make a bigger difference than 20uf. Keep in mind those old caps are probably out of spec, so the old caps on one side most likely won't compare to the new caps on the other side even if replacing with the save value.

If it were me I'd replace the old 200uf/10v, 15v's with 220uf 16v or 25v and do both sides straightaway. That's a very common value and you should have NO trouble getting the quality cap of your choice. Looks like you're dealing with polar electrolytics; in those values, I like Panasonic FR or FM, other people are big Nichicon fans, both are very good. Whatever your brand, I would pick a good, high-temp, low ESR cap with a decent service life rating and call it good.

I say if you're gonna do it, just get it done, and if you're ordering all the caps you need at once from the likes of Mouser/Digikey, you'll get substantial discounts at certain quantity points, so there's not much sense in only doing a little bit at a time--just getting a handful at a time will cost more in the long run. When ordering my console caps, it was a real hoot watching the total price go DOWN as I added more of a given value to the order as I kept hitting those quantity discounts! I actually did quite a bit of consolidating values in order to take advantage of quantity discounts as well. I was ordering anywhere from dozens to hundreds to thousands of a given value of cap so in my case it made lots of sense. YOUR mileage my vary, but I had no trouble replacing 10uf, 15uf, 22uf and 47uf all with 47uf, and combining 100uf/16v and 220uf/16v and 25v all to 220uf/25v, for example. This saved lots of money, simplified the job some, didn't cause any trouble in my circuits and indeed, as Cory suggested, there were service bulletins for my console where the manufacturer themselves had suggested increasing some of those values anyway. Win-win! Again, I can't speak for your machine directly, not sure about any changes your machine's mfr might have made during the model run. My little anecdote here is just to illustrate that unless someone sees something about that schem that suggests I'm wrong here, you should have some play in what you can re-cap with and with a bit of shopping savvy you can streamline the order.


Good luck, have fun!

 

[JDMiller1988]

Cool. looks like I am getting closer and closer here. Hopefully I will be ordering the caps soon, have a nice cart going at mouser.

So whats the point in having a bunch of 200uf caps with slightly different voltage ratings 10-20? I mean couldn't they have just done them all 200uf 20v and been good (if not better).

Thanks!

 

[sweetbeats]

Where they are 20V they needed to be 20V, where they are 10V they saved money by getting the 10V. They weren't getting onesy-twosey like us and trying to get at least 10 or 25 pieces of one value to get a price-break...they were buying caps by the tens of thousands. In some cases it may have also been a physical space limitation.

+1 to what Brian said about doing both sides. matched value or not it is not likely to perform the same once you recap because cap quality and performance are significantly different today as compared to the parts that are in there, AND what's in there is aged.

Whether or not you hear the difference I don't know because those 200uF caps aren't in the audio path.

consider replacing all the 10uF caps with 47 or 63uF parts.

 

[JDMiller1988]

I will definitely be doing both sides thanks to your guys input. Most the parts I am looking at are smaller (not too much) than originals even with higher value, (my how we have advanced in a few years) so I shouldn't run into too many size constraints.

And on upping the 10uf caps, are there places that I shouldn't be changing around values too much?

 

[sweetbeats]

Let me put it this way...you'd be totally fine leaving the 10uF caps as they are, or you can increase them.

I'd have to look at other cap values. I specifically honed in on the 10uF caps because those are coupling caps in the audio path. Capacitors act as a natual lo-cut filter. This can be very useful and desirable in many places, but the knee point on a 10uF cap is a little high IMO. Still below the human range of hearing but still too high in the signal path. An electrolytic cap in the audio path is always a compromise between hi frequency performance limit and lo frequency performance limit. The bigger the cap's value the better the LF performance at a sacrifice to the HF performance. BUT...today's electrolytic capacitors have much better HF performance so it is not as risky to go a bit bigger in the value to maintain LF performance while not sacrificing HF performance. That's the deal. So, again, you'd be totally fine keeping it 10uF.

Specifically, I’m talking about C101, C104, C105, C108, C109, C112...maybe others but I can't tell because the schematic is cut off...

 

[JDMiller1988]

Got the new caps in the mail today and the only one I couldn't match really close was the 350uf 10v, I ended up getting a 390uf 16v, I'm not asking for trouble putting that in am I? Shouldn't take too long to get the broken side recapped.

 

[briank]

Got the new caps in the mail today and the only one I couldn't match really close was the 350uf 10v, I ended up getting a 390uf 16v, I'm not asking for trouble putting that in am I?

Don't sweat it!

Have fun!

 

[JDMiller1988]

Alright got em all in, pretty simple really. The copper foil circuit was a little delicate, but I got them all in fired it up and am now listening to some recordings I did. Gotta say, I missed this machine, it sounds great and is really nice to use.

Anyhow, all the old wooshy sounds are gone and it has sufficient gain. Thanks to everyone that helped with info. I am going to recap the other side soon.

The gain still has a noticeable difference on either channel, along with a dimmer light bulb (possibly a different bulb). I am not sure if it recapping will effect the bias, but I am not going to worry about that until I recap the other side. If had some tantalum caps inside, I didn't think those were around in the mid 60s, also they were way above spec, same on both side, maybe this has been serviced before.

Thanks again for all your help, forums are a wonder of the modern world, truly awesome!

 

[briank]

Boy do I wish my console re-cap would go that quick!

Great to know they went in with no probs!

 

[sweetbeats]

Yeah, congrats. That's great.

IIRC the 390uF cap is a local filter cap and you'll be fine going from 350uF to 390uF.

I think that's cool that your deck has UV light meters in it...how do you monitor the sound level though?

 

[JDMiller1988]

Haha, like I was saying it seems like they did things a little different back then

I am going to recap the other side and the motor control section (this is where the cap with its guts falling out is)

Then maybe try to get both sides working the same, then I'll post some pix and maybe some recordings.