We'll know why it does this when it's fixed, but you'll have to keep it on the bench and wait until it fails.
I just fixed an smt preamp that worked ok on turn on, and then drifted up to the positive rail over a couple of minutes.
Turned out to be a bad solder joint at the op amp input.
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Roger that. I kept it hooked up for at least a week when I first started this thread.........put like 80-100 hours on it and no fault.....so I buttoned it up and it's been fine since.....until today.
I plan to leave it open for now until the problem shows up again, no matter how long it takes.
Rayma, thank you so much for your insight and time, it means a lot to me.
Thanks, these things seldom go away by themselves. Keep us informed.
You might ask McIntosh tech support if they've seen a similar problem.
I did inform Mcintosh of the issue, they have never encountered this problem before.
From customer support: "you might want to try and replace the JFETS for that channel or try and disable he post attenuator circuit all to together by removing C1 and C37 for both channels. Maybe even the post attenuator IC if it is in a socket. The only thing you may hear is slight popping when the volume is adjusted and the volume control IC is stepping up or down the volume level. This might be your best option for a long term test of such an issue."
From customer support: "you might want to try and replace the JFETS for that channel or try and disable he post attenuator circuit all to together by removing C1 and C37 for both channels. Maybe even the post attenuator IC if it is in a socket. The only thing you may hear is slight popping when the volume is adjusted and the volume control IC is stepping up or down the volume level. This might be your best option for a long term test of such an issue."
The -12db post attenuator kicks in @ 77 on the volume control.
-9db @ 83
-6db @ 89
-3db @ 95
So I don't actually think it is the post attenuator network anymore since the fault was happening at volume control levels <64
-9db @ 83
-6db @ 89
-3db @ 95
So I don't actually think it is the post attenuator network anymore since the fault was happening at volume control levels <64
I think I tracked down the culprit for those who are interested.
I have been using the preamp as a headphone amp late at night to try and put more hours on it and it payed off. The right channel crapped out on me at around 2am. So I put a 1V 1kHz through it and tracked it down to the Digital volume control IC20 (CS3310-KP), pin 9 had 1V but there was 0v on pin 11. Left channel's pin 16 and pin 14 were fine, 1V at pin 16 and when I turned the volume control up and down pin 14 would correlate with what I was doing, but nothing on pin 11. I sprayed IC20 with some freeze spray and the right channel instantly started working fine.
I might re-solder IC20 and see if everything is fine for the next couple of months. I was going to just order a CS3310-KP but all I can find is surface mount, nothing in DIP.
Hopefully this has been the end of an annoying issue🙂
I have been using the preamp as a headphone amp late at night to try and put more hours on it and it payed off. The right channel crapped out on me at around 2am. So I put a 1V 1kHz through it and tracked it down to the Digital volume control IC20 (CS3310-KP), pin 9 had 1V but there was 0v on pin 11. Left channel's pin 16 and pin 14 were fine, 1V at pin 16 and when I turned the volume control up and down pin 14 would correlate with what I was doing, but nothing on pin 11. I sprayed IC20 with some freeze spray and the right channel instantly started working fine.
I might re-solder IC20 and see if everything is fine for the next couple of months. I was going to just order a CS3310-KP but all I can find is surface mount, nothing in DIP.
Hopefully this has been the end of an annoying issue🙂
Unless the soldering is poor, resoldering is not likely to fix it. But it may well mislead you - the disturbance may make the chip (if faulty) come good, but only for a while.
Use solderwick to clean all the solder off each pin and use Safewash or other citrus-based solvent to get rid of the flux. Rinse carefully with distilled water. Then resolder.
CS33310KP is available in DIP, one-off quantity, from the British company Little Diode - check their website. It's also advertised on eBay.
Use solderwick to clean all the solder off each pin and use Safewash or other citrus-based solvent to get rid of the flux. Rinse carefully with distilled water. Then resolder.
CS33310KP is available in DIP, one-off quantity, from the British company Little Diode - check their website. It's also advertised on eBay.
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Hello Keit,
Are you suggesting doing this before replacing it? I see Little Diode does sell it from UK, seems like that could get very expensive to replace if I get it from them. I did contact McIntosh Labs and gave them their own part number, hopefully they have a bin of them laying around and are willing to sell one to me, they are a lot closer to me than England is.
Disagree - the fault may well be a cold solder joint, and following your procedure ( 🙂 ) is the only (and cheapest) way to find out.
If the fault returns, THEN consider replacing it.
Hi Cliffforrest,
I completely agree, it isn't much work to remove the IC if the fault occurs again after resoldering.
McIntosh did respond, and really fast too! Seriously it was only 5 minutes after I emailed them, that to me is good customer service. Anyway they told me that the replacement part is different but only gave me a different McIntosh part number. The number I gave them which was in the service manual was #133331, the part they replace it with is #133637. Is there an equivalent to the CS3310-KP that anybody knows about?
Hi Ray,
Thanks, I saw that one on Ebay too. Not gonna lie here, I am a little leery of ordering from China on Ebay.
I have been poking around datasheets trying to find a suitable replacement and came across one from Texas Instruments. Would anybody care to advise me if this is will work? On paper they look very similar, the PGA2311 has less input capacitance and larger bandwidth.
Here is what inside now:
http://www.mouser.com/ds/2/76/CS3310_F1-18400.pdf
Here is what I am looking at:
http://www.ti.com/lit/ds/sbos218a/sbos218a.pdf
PGA2311P Texas Instruments | Mouser
-bird
Thanks, I saw that one on Ebay too. Not gonna lie here, I am a little leery of ordering from China on Ebay.
I have been poking around datasheets trying to find a suitable replacement and came across one from Texas Instruments. Would anybody care to advise me if this is will work? On paper they look very similar, the PGA2311 has less input capacitance and larger bandwidth.
Here is what inside now:
http://www.mouser.com/ds/2/76/CS3310_F1-18400.pdf
Here is what I am looking at:
http://www.ti.com/lit/ds/sbos218a/sbos218a.pdf
PGA2311P Texas Instruments | Mouser
-bird
PGA2311 is designed to be FW and HW compatible, and buying TI from Mouser is a safe enough route.
I would renew the 10uF electrolytics around this chip at the same time.... the quality of some recent elcos is worse than ever. Mouser sell Nichicon VR (search Mouser 647-UVR to see them) - use these with confidence.
I would change these few caps, because the volume level is stored in a static (soft) register, and could be corrupted by transients.
I would renew the 10uF electrolytics around this chip at the same time.... the quality of some recent elcos is worse than ever. Mouser sell Nichicon VR (search Mouser 647-UVR to see them) - use these with confidence.
I would change these few caps, because the volume level is stored in a static (soft) register, and could be corrupted by transients.
Thanks Rod, to be clear here FW is firmware and HW is hardware? If the PGA2311 is truly compatible I would be a happy camper🙂 Also good advice about replacing the caps surrounding the IC.
I am waiting for a call back from the parts department at McIntosh about their replacement part, #133637. I am sure they won't disclose the actual device model number over the phone to me but it can't hurt to ask, for I would like to see what they are using for replacements now. If the price isn't outrageous from McIntosh I might just order it from them. Methinks they superseded the old Cirrus Logic part because either they are not available in a DIP package anymore, or they are faulty. Another thing I noticed is that the PGA2311 has a better temperature rating, might be good in a tube preamp😉
I am waiting for a call back from the parts department at McIntosh about their replacement part, #133637. I am sure they won't disclose the actual device model number over the phone to me but it can't hurt to ask, for I would like to see what they are using for replacements now. If the price isn't outrageous from McIntosh I might just order it from them. Methinks they superseded the old Cirrus Logic part because either they are not available in a DIP package anymore, or they are faulty. Another thing I noticed is that the PGA2311 has a better temperature rating, might be good in a tube preamp😉
Yes, that's right.
The TI version's application schematic is also effectively the same, though it is improved by not requiring power sequencing (VA+ before VD+) that the CS3310 does, and does not show a VA+ to VA- cap. TI make things that work, IME.
I see that now when comparing "Power up Considerations" on pg.9 of the 3310 datasheet and the "Power-up Reset" mode on pg.7 in the PGA2311 datasheet. I like what the PGA2311 has to offer and feel confident enough to go ahead and just replace the CS3310 with the PGA2311.
What I am suggesting is:-
a) Inspect the soldering carefully. Unless your eyesight is very good, you will need a magnifying glass or jeweller's loupe. With the dip soldering used with mass produced pcb's, and the perfection of this technique in the 1970's, soldering is seldom at fault.
b) But I agree with Cliff Forrest - a soldering fault is still a possibility, and ordering a new IC may be unnecessary - but see below.
c) Be aware that resoldering may cause internal disturbance in the IC and that may make it come good. But only for a while.
d) My backgroud is in servicing professional equipment. We work to higher standards than your run of the mill consumer gear tech of past days. Company policy was in cases like this, replace the chip regardless, due to issues (b) and (c). It avoids customer complaint and does not require lengthy soak testing.
Interesting comment about purchasing from UK vs purchasing from USA. In my country (Australia) the population is too small to make local parts stocking viable, except for the most common types of parts. So, we purchase a lot from firms in USA, UK, Germany. This is my experince, consistent over decades:-
UK firms: pricing good, shipping costs to Australia low. Service not good - difficult to resolve complaints eg for wrong parts sent. Invoicing inaccurate.
USA firms: pricing usually good. Shipping to Australia very expensive (why?). Mistakes in shipping and inviocing very rare.
German firms: Not very diffrent to USA firms.
In all cases, USA, UK, and German firms ship faster than Australian firms. Interesting fact: I have started buying from Chinese firms. Service good, pricing ggod, can be cheap, shipping is often free. Often the goods turn up having been supplied from an Australain warehouse! However, product quality can be low.
a) Inspect the soldering carefully. Unless your eyesight is very good, you will need a magnifying glass or jeweller's loupe. With the dip soldering used with mass produced pcb's, and the perfection of this technique in the 1970's, soldering is seldom at fault.
b) But I agree with Cliff Forrest - a soldering fault is still a possibility, and ordering a new IC may be unnecessary - but see below.
c) Be aware that resoldering may cause internal disturbance in the IC and that may make it come good. But only for a while.
d) My backgroud is in servicing professional equipment. We work to higher standards than your run of the mill consumer gear tech of past days. Company policy was in cases like this, replace the chip regardless, due to issues (b) and (c). It avoids customer complaint and does not require lengthy soak testing.
Interesting comment about purchasing from UK vs purchasing from USA. In my country (Australia) the population is too small to make local parts stocking viable, except for the most common types of parts. So, we purchase a lot from firms in USA, UK, Germany. This is my experince, consistent over decades:-
UK firms: pricing good, shipping costs to Australia low. Service not good - difficult to resolve complaints eg for wrong parts sent. Invoicing inaccurate.
USA firms: pricing usually good. Shipping to Australia very expensive (why?). Mistakes in shipping and inviocing very rare.
German firms: Not very diffrent to USA firms.
In all cases, USA, UK, and German firms ship faster than Australian firms. Interesting fact: I have started buying from Chinese firms. Service good, pricing ggod, can be cheap, shipping is often free. Often the goods turn up having been supplied from an Australain warehouse! However, product quality can be low.
If I was running a business and it was a customer, I couldn't agree more, replace it and be done with it.
But I am not, so I do have some options. Besides I am a curious fellow that would like to see how long she runs without breaking again after removing, cleaning and resoldering it back in. I get it, the heat could internally "fix" the issue temporarily inside the IC, either way we will know if it is the IC when and if it breaks again. What I plan to do is write down the IC and caps I need and get them the next time I have to order some parts for a project or whatever. When they arrive I will put them in a baggy and mark them accordingly. If and when the preamp breaks again I will just remove and replace the components. My friend (the owner) was thinking of selling the unit, but he has grown to like it and will probably hang on to it for another couple years. I will ring him later and tell him the news and for all I know he might just say order the darn parts and just replace everything lol. He is the one in the first place that wants me to replace all the electrolytic caps in the signal with audio grade ones.
But I am not, so I do have some options. Besides I am a curious fellow that would like to see how long she runs without breaking again after removing, cleaning and resoldering it back in. I get it, the heat could internally "fix" the issue temporarily inside the IC, either way we will know if it is the IC when and if it breaks again. What I plan to do is write down the IC and caps I need and get them the next time I have to order some parts for a project or whatever. When they arrive I will put them in a baggy and mark them accordingly. If and when the preamp breaks again I will just remove and replace the components. My friend (the owner) was thinking of selling the unit, but he has grown to like it and will probably hang on to it for another couple years. I will ring him later and tell him the news and for all I know he might just say order the darn parts and just replace everything lol. He is the one in the first place that wants me to replace all the electrolytic caps in the signal with audio grade ones.
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