Basic C2 Restoration

Hooked it up to the M1 and listened to my standard discs.Sounds very nice, yet not quite as detailed as some of my other equipment. Mind you, these are minor differences and from memory which is notoriously faulty regarding music. That's why I control for that as best as possible by listening to specific discs and tracks from them. Since I don't know this unit's history, I don't know whether it's been sitting idle for awhile and just needs to burn in again, or whether this is as good as it gets with the current caps and opamps. Haven't tried it with vinyl yet, but that will have to wait til I get back from my next trip to GVA. I'd still like to know a little more about the caps that are currently installed, whether original or replaced at some point.
 
Thanks for the info, but mine already has the 9V version and it works fine. The question I posed earlier in the thread was based on rebuilds I've read on the net, in one of which the OP stated he thought that the C2 used a 12V vs the C1's 9V. That's why I wanted to check and see if anyone else had read that or knew from part numbers etc. The known issue of overvolting one of the opamps made me wonder if the same thing was happening in the protection circuit to the relay.

The loudness button issue was simply due to the faceplate not being secured when I did that initial listen. I had just pressed it into place, but not fastened it with the screws. So, I wasn't able to push the loudness button fully to engage the catch mechanism. Works fine, but the sound still seems tubby to me. Other units' circuits implement the loudness function better.
 
I think you have original caps. I have the same type of Elna caps in a little 75 WPC Yamaha receiver. I've also seen these in other older amps. I don't know how one would order new caps without knowing the series number. All I see on these guys are a circle and a letter inside. Without the decoder ring we will never know what they are.

In the Yamaha amps I had with these I think things started to smooth out after about a week of 24/7 use. Just tune in a nice radio station and let it play away.


I don't see anything to indicate the series of these caps.

DSCN3604.JPG
 
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Interesting. The other photos I've seen of the insides of this amp show black and grey cap sleeves IIRC. I suppose if it was in production long enough, cap series could have changed to what was available at the end of the run. The mid 80's H/K gear I've worked on had Elna red sleeve with gold lettering audio caps in the phono circuit, and I have worked on something that had the darkish blue/grey sleeve. The Basic M1 and T2 I've worked on didn't have caps with these sleeves, so not sure quite what's going on. The plot thickens...

BTW, what model Yammie and what year was it from?
 
It is just a simple RX 496 from the late 90s but for $29.99 it rocks really well.

Elna had a lot of funny color schemes back in the 90s. Elna Starget caps had a whole bunch of different colors. I think Cerifine had gold on red at one point.

Here is a pic of a pre amp in a Sony STR 30 ES from the late 90s. It has red color Elna caps that look like some of the Starget caps but it only has the letter in the circle to tell you what it is.

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Plus a couple questions...

I just received this and it appears to be in great shape, though I haven't plugged it in yet for some basic testing/listening. I'm not sure how much of a restoration this will get as I'm a bit puzzled by what I see inside. As compared to other threads and photos I've come across of this unit, though mine appears to be original, the caps look to have different sleeves. So, I'm actually not sure if it's already been recapped or not, hence the questions before I get started.

The majority of the caps have brown sleeves with white markings, like Silmic IIs, however, there is no Silmic marking, nor any other series marking like RA3 or other Elna cap markings I could find for brown sleeved caps. They are all 85 C rated and the 2200uF/6.3V caps C5,6 even look to have a clear glue at the base. The other caps, to include the BPs have a dark blue-grey sleeve with white printing.

The other issue I came across while unpacking was a rattling sound. Turned out to be a 1uF/50V BP cap with one leg completely torn off at the seal (can't even see any metal in the lead hole). The other leg doesn't appear to even have solder residue, but is spread out almost perpendicular to the base of the cap as if used as a bypass and had to be stretched to span whatever it was bypassing. I don't see any listing in the SM for BP caps of this value, so perhaps someone did work on this before. (?) This is the main reason for no power-up yet, though I do have a DBT I'll use first. Since you have to disassemble to get at the trace-side, I haven't done a visual of it to see if I can spot where it may have been attached. Suppose it could have been in since production?

The relay is a 9V Omron, though I read somewhere this unit used a 12V relay. Confirmation?

Anyway, I wanted this to complete my set since I rebuilt a Basic M1 (Ugly Betty) and recently acquired and recapped a Basic T2. Paid a little more than I wanted to, but c'est la vie.

Pics to follow once I set up the tripod and lighting.

I am willing to bet this your broken lead Cap. Thiis is mine.C2 Back panel Non Polar Cap.PNG C2 Back panel Non Polar Cap AK.PNG This is yours. It is very easy to break the lead when the unit is disassembled.
Hope that helps.
 
OK, that makes sense. I didn't even realize there was a cap that was supposed to go there. What's the purpose? Filter input noise?
 
When I did my re-cap I replaced that screw with a old copper/brass bolt and nut with washers. Soldered on the other side of the output. I am far from an expert but I would think you are right. A way to connect the chassis to the ground on the outputs. May be for static build up or for safety in case one of the jacks comes loose. I would like it if someone (Leestereo) who knows this stuff chimes in because I am curious as well.
OK, that makes sense. I didn't even realize there was a cap that was supposed to go there. What's the purpose? Filter input noise?
 
Finishing my mouser order for multiple projects and thought I'd add the caps and miscellany for this pre. Only ones I don't have in stock, but it got me thinking about the oudness button and the frequency boost. Since it sounds a little tubby, I wondered what values would need to change in the circuit for the r/c filter that seems to be set up at S4, the loudness button.

The owner's manual states the boost is +6dB / +9dB at 100Hz for a reference volume of -30dB / -40dB respectively. Looking at the scat, it appears that when the loudness switch is engaged, an r/c filter consisting of 0.027uF/24K ohms is used (C27,28 R65,66). What value changes will move the frequency boost to say 50Hz to get less tubbiness? I've tried some online calcs, but not sure I'm inputting proper numbers.
 
Started the rebuild while waiting for my order to show up as I have most of the parts on hand. All the 1uF/50V 'lytics are being replaced with film caps. The main filters were replaced with 1000uF/50V Nichicon HE series with 1uF/63V film bypass caps underneath. I also decided to replace the rectifiers with UF4004s vs the standard recovery OEMs. Though I haven't definitely decided to do so, I may replace some of the resistors directly in the signal path with Dale RN60Cs. Pics to follow.
 
Some shots of boards pre work during disassembly:

Control Board
30126660063_c7b92d9526_o.jpg


Filter Board
30673842301_125fd33b8c_o.jpg
 
Finishing my mouser order for multiple projects and thought I'd add the caps and miscellany for this pre. Only ones I don't have in stock, but it got me thinking about the oudness button and the frequency boost. Since it sounds a little tubby, I wondered what values would need to change in the circuit for the r/c filter that seems to be set up at S4, the loudness button.

The owner's manual states the boost is +6dB / +9dB at 100Hz for a reference volume of -30dB / -40dB respectively. Looking at the scat, it appears that when the loudness switch is engaged, an r/c filter consisting of 0.027uF/24K ohms is used (C27,28 R65,66). What value changes will move the frequency boost to say 50Hz to get less tubbiness? I've tried some online calcs, but not sure I'm inputting proper numbers.

I really would have no clue. I would say the same about the amp as well that is when I tried the loudness button anyway. The loudness control is something I never use on any of my equipment but I would like to know what you come up with.
 
I finished slinging solder last night (last of the parts arrived...wasn't expecting them til Tuesday or so), but still have to clean the switches. So, no listening yet. I followed many of Leestereo's recommendations in his Basic C1 restoration re. zeners and C0G caps, and new opamps (with sockets) but went a bit further and also swapped out resistors for ones in the signal path. I used the mil-spec Dale RN60Cs mentioned earlier and also the industrial equivalent CMF60s which are very quiet and allow a lot of detail through. I'm not as well versed in describing what was done, but did label the shots and also circled key components on the schematic sections for any who want to follow along. I kept the cap values the same vs bumping some up in power supplies, etc and mainly used Panasonic FM and Nichicon HE series for most caps. The BiPolars got swapped for Nichicon Muse ES, though the EQ Amp (phono) got RBS Silmic bipolars (3.3uF/50V) since that's what I had on hand. All the 1uF 'lytics got changed to Kemet films, and the head amp got a pair of Silmic IIs for the 10uF/25V spots. Here's some shots along with the scats of each area.

Filter Board
One quick note here: I didn't have EXACTLY 3K resistors, so I used 2.94K at R37, 38 and 3.05K at R39, 40.
30926368736_0869c77ff2_o.jpg

22783337508_43ff50863d_o.jpg


Head Amp

The NJM2068 opamp also came in a SIL format, so I ordered one for the headphones as the linked info provided by Lee was based on a headphone amp usage to begin with.
25326056939_9bd535d62a_b.jpg

30961974815_f84bc348f3_z.jpg


Tone Board
One note: I mis-labeled one R...R31 should read R34 and I forgot to circle the other half of the opamp on the scat.
30962028935_705a484089_o.jpg

30961973685_85437e6137_b.jpg


More to come...
 
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The main CB to include the Flat Amp, EQ Amp (Phono) and Power Supplies. D11-14 (20V zeners) replaced with 16V zeners for the opamps.

30926408386_1f380c69ef_k.jpg


Flat Amp
30961976045_e657b77a67_b.jpg


EQ Amp
30961974335_8df6be9507_b.jpg
 
I finished slinging solder last night (last of the parts arrived...wasn't expecting them til Tuesday or so), but still have to clean the switches. So, no listening yet. I followed many of Leestereo's recommendations re. zeners and C0G caps, and new opamps (with sockets) but went a bit further and also swapped out resistors for ones in the signal path. I have a bunch of mil-spec Dale RN60Cs which are very quiet and allow a lot of detail through. I'm not as well versed in describing what was done, but did label the shots and also circled key components on the schematic sections for any who want to follow along. I kept the cap values the same vs bumping some up in power supplies, etc and mainly used Panasonic FM and Nichicon HE series for most caps. The BiPolars got swapped for Nichicon Muse ES, though the EQ Amp (phono) got RBS Silmic bipolars (3.3uF/50V) since that's what I had on hand. All the 1uF 'lytics got changed to Kemet films, and the head amp got a pair of Silmic IIs for the 10uF/25V spots. Here's some shots along with the scats of each area.

Filter Board
One quick note here: I didn't have EXACTLY 3K resistors, so I used 2.94K at R37, 38 and 3.05K at R39, 40.
30926368736_0869c77ff2_o.jpg

22783337508_43ff50863d_o.jpg


Head Amp

The NJM2068 opamp also came in a SIL format, so I ordered on for the headphones as the linked info provided by Lee was based on a headphone amp usage to begin with.
25326056939_9bd535d62a_b.jpg

30961974815_f84bc348f3_z.jpg


Tone Board
One note: I mis-labeled one R...R31 should read R34 and I forgot to circle the other half of the opamp on the scat.
30962028935_705a484089_o.jpg

30961973685_85437e6137_b.jpg


More to come...
Mine is sitting on top of one of my SRS2 Polks right now. I still do not like the sound and I have to turn the volume up way farther than I should to get it up to a decent listening level. Time to go back in and fish around will come soon. I really appreciate all the images John.
 
I still do not like the sound and I have to turn the volume up way farther than I should to get it up to a decent listening level..

Could be a ground issue. Check all the solder joints at the volume pot and elsewhere. Even the screws holding the CB down,.
 
Switches and pots are all cleaned and lubed as appropriate with D100, D5, F5. All the boards are back in, chassis screwed together, and it passed the DBT with flying colors. Initial listening impressions are an overall clean sound, perhaps a touch brighter than before the recap and with maybe just a little more detail, but since the project took longer than expected (due to placing a second order for some items I didn't realize I was missing, and deciding to change out the ceramic caps, opamps, etc,) I really can't say that this was a stunning improvement or anything like that. The restoration certainly didn't harm the sound, and corrected the known problems of over-volting the opamps, the balance pot issue, weak solder joints on the input jacks, etc. and now the caps are fresh for another 30 years or so. It will be interesting to see if there's any sonic changes over time as the caps "burn in" while I listen or whether it's all psychoacoustic (and does it matter since I won't know either way). Now to just get the finishing touches...cleaning the faceplate, knobs, push-buttons, and put the cover back on. I need to also bring the T2 I recapped and put it in the stack for a full Kenny Basic system.
 
All the pieces of the stack together. the tuner and pre are in pretty good cosmetic shape. Betty's seen better days, but it's what's on the inside that counts right?

BasicT2, Basic C2, Basic M1 "Ugly Betty"
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Well, I've done a bit more listening and today put it in our main system in place of my Rotel RC-1070. It's controlling a NAD C270 and running restored AR-3a speakers. There's definitely no lack of bass with everything flat! I was finding in my test area in the basement having to bump up the bass a little when running EPI 100s. It's dead quiet. I'm listening to Michael Hedges "Aerial Boundaries" right now and earlier listened to a bit of Craig Chaquico's "Acoustic Highway". I must say that my earlier quick assessment wasn't fair. The layering in "Gypsy Nights"...I was definitely hearing some parts that I hadn't heard before. And the attack of Hedges' plucking style is outstanding. Going back over some earlier notes in the thread, there's no lack of detail now, though source material limitations will be revealed for sure. House is getting a bit noisy now for more critical listening, but I'm more than pleased with the restoration.
 
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