Courtiestown - Naim Amplifier (Avondale) Upgrade Project

[Richard Lines]

I wouldn't worry to much about those caps, the feedback one has the biggest influence and as long as their axial tants above 100uF your ok, Les uses films for inlet and that's what I use but tried allsorts and its small differences, the 68uF across the bias transistor has very little influence I have a 47uF axial tant just like the one you have in feedback and that works great, think Les uses tant beads here now just like Naim.

I know in the past that Les recommended Kemet SMR's on the inlet side for Naim modifications - https://uk.rs-online.com/web/p/film-capacitors/1719416

You're suggesting going over 100uF for C6???

Regards

Richard

 

[GWM]

Yea feedback cap which is the 47uF one you have now should bigger the improvement to Bass is obvious especially quality,no problem with 47 just bigger is better, I actually have 220 in there now on my Qudos boards.
My earlier NCC200 boards I got from Les came with 120uF caps supplied by him.

 

[Richard Lines]

Good Evening All,

A quick look on the Farnell site shows the "cheapest" 120uF tantalum capacitor is https://uk.farnell.com/kemet/m39003-03-0260/cap-120uf-20v-tant-axial/dp/3017170?st=120uf at a mere £25.92 each, RS only show two SMD devices, Mouser have a wet device https://www.mouser.co.uk/ProductDetail/Vishay/135D127X9050F6?qs=qJDCoXOHpuFmc3bqB6LtEg== at £52.78 and at DigiKey https://www.digikey.co.uk/en/products/detail/kemet/T110C127K010AS/12502329 a suspiciously cheap offering at "only" £10.91...........

Regards

Richard

 

[chiily]

I've bought 10 NCC200 v1.5 boards off Avondale to change out all my amplifiers so, in a perfect world, 10 please, but anything would be a start. Worst case is I parallel up 3.3 or 4.7uF versions.

Regards

Richard

I could probably find ten by de-soldering them from old naim pre-amp line boards I have, if you really need them, FoC of course

Just let me know.

 

[GWM]

Good Evening All,

A quick look on the Farnell site shows the "cheapest" 120uF tantalum capacitor is https://uk.farnell.com/kemet/m39003-03-0260/cap-120uf-20v-tant-axial/dp/3017170?st=120uf at a mere £25.92 each, RS only show two SMD devices, Mouser have a wet device https://www.mouser.co.uk/ProductDetail/Vishay/135D127X9050F6?qs=qJDCoXOHpuFmc3bqB6LtEg== at £52.78 and at DigiKey https://www.digikey.co.uk/en/products/detail/kemet/T110C127K010AS/12502329 a suspiciously cheap offering at "only" £10.91...........

Regards

Richard

Check out eBay that's where I get tants from, the usual electronics stockists are to expensive.

 

[Richard Lines]

Check out eBay that's where I get tants from, the usual electronics stockists are to expensive.

I normally do, that's how we ended up with 1000 x 47uF/ 50V wet tantalums.................... back when we were buying and selling stuff. I'm slightly more wary of what I'm buying to stick on these boards overall was in my mind at the same time as well.

Just on with bottoming out "differences" between the circuit diagram, PCB and BOM. I see C8 has crept up to 68pF (from 47) in value on v1.5, not a biggie but just getting the BOM up to date. The circuit diagram shows a 1k2 going to the trimmer wiper which is showing as a 2k2 on the PCB (and BOM). Changing out the silver mica for polystyrene but for the one remaining 47pF (now 68pF) as per what is written on the circuit diagram. I'm assuming R7 2k7 in the BOM is the 3k0 on the PCB (by a process of elimination).

Regards

Richard

 

[GWM]

Use the 1.2K on the trimmer I found on one board I ran out of adjustment to get the correct bias with 2.2K.The rest doesn't matter the 68pf was about availability if you can find 47 then OK but not lower.

 

[Richard Lines]

Use the 1.2K on the trimmer I found on one board I ran out of adjustment to get the correct bias with 2.2K.

That's useful to know....

Regards

Richard

 

[337alant]

I normally do, that's how we ended up with 1000 x 47uF/ 50V wet tantalums

2 parallel 47uf wet tants would be ideal if you still have some ?

Alan

 

[337alant]

One VBE typically power one amp module's input stage. That VBE needs a 50-0-50VAC transformer (or thereabouts).

50V secondary gives 70V DC, 42-0-42VAC transformer works fine in my experience (59VDC), the VBE is more like a filter than a reg and the drop out is only 2-3v, and the front end draws less than 20mv
You set the output voltage with the Zener diodes so the higher the secondary the bigger the voltage drop and the more heat you have to dissipate

Alan

 

[Richard Lines]

2 parallel 47uf wet tants would be ideal if you still have some ?

More than enough to supply the 20 I'll need across the 10 boards that's for sure.

Regards

Richard

 

[Richard Lines]

Good Morning All,

Has the world gone barking mad??? OK so RS are a big supplier;

https://uk.rs-online.com/web/p/through-hole-resistors/4639494 - handily available in a bag of 100!!!!!

but, wait for it, even Rapid are at it;

https://www.rapidonline.com/1-metal...andling":["0.6W"],"Resistance":["3kΩ"]}

That's the way to encourage the hobby market, err not.

Regards

Richard

 

[337alant]

You sometimes find they have multiple listings for the same products but with different package options like minimum package 1 , 10 ,100, 1000
here is a pack of 10 for a 3k0 0.6W TE metal film which are very good.
LR1F3K0 | TE Connectivity 3kΩ Metal Film Resistor 0.6W ±1% LR1F3K0 | RS Components (rs-online.com)

Alan

 

[Richard Lines]

You sometimes find they have multiple listings for the same products but with different package options like minimum package 1 , 10 ,100, 1000
here is a pack of 10 for a 3k0 0.6W TE metal film which are very good.
LR1F3K0 | TE Connectivity 3kΩ Metal Film Resistor 0.6W ±1% LR1F3K0 | RS Components (rs-online.com)

Alan - I did find those but passed them over for these - https://uk.farnell.com/te-connectivity/lr2f3k0/res-3k-1-750mw-axial-metal-film/dp/2330331 - which are 0.75W devices at least. At one point I was looking at buying 1k5 to put in series.

I note that Farnells have the CAP6 diode on "clearance" at £1.92 - https://uk.farnell.com/taiwan-semic...ectifier-20a-200v-to/dp/2677438?st=mbr20200ct or buy it from Mouser - https://www.mouser.co.uk/ProductDetail/Taiwan-Semiconductor/MBR20200CT-Y-C0G?qs=mAH9sUMRCtsMYaWWNaBazg==&gclid=EAIaIQobChMI1Z6F_Jjh9AIVXoBQBh1DLAgCEAAYAiAAEgL_FPD_BwE at £1.03

I see both diodes for the HackerCap are on back order at Farnell.

Regards

Richard

 

[337alant]

Changing out the silver mica for polystyrene but for the one remaining 47pF (now 68pF) as per what is written on the circuit diagram

I wouldn't do that, this is the "dominant pole" capacitor and high stability is what the Silver Mica cap is very good at !

Alan

 

[Richard Lines]

I wouldn't do that, this is the "dominant pole" capacitor and high stability is what the Silver Mica cap is very good at !

Alan

Alan - I'll re-phrase what I said. There is a note on the schematic stating that all "*" capacitors are to be polystyrene. C8 itself is clearly marked as being "ceramic or silver mica".

In all three reading through 765 pages of the D.I.Y section I note a comment from LesW;

LesW mentioning that silvered micas are great for decoupling HF in the context of transistor base-capacitors

I also read the post about somebody who powered the board up with this capacitor absent.

Regards

Richard

 

[Richard Lines]

Good Afternoon,

Well that's me back on dry land.

A box arrived from Avondale today:-

As have two, to be investigated, Terry Pardo STR's.

With a whole host of parts here there really is nothing stopping some aspect being worked on.......

Having 'catalogued' the various bits ordered for this project I set about measuring the two batches of BC546B's I've got. One lot from Farnell and the other off a well known internet auction site:-

The candidates for TR1 and TR2 are pretty obvious as there is more than 10% difference....

Some of you should recognise the tantalums in the next photo, these are all we have left of batch of 1000:-

No shortage of choice for C6 there.

Regards

Richard

 

[Richard Lines]

Good Evening All,

That's my cataloguing of various electronic bits wot I have ordered previously done and, being honest, I'd forgotten about some.

Starting with Exhibit A:-

I have absolutely no idea where I got them from. I thought everything was filed in Outlook somewhere. These would have been bought at a time when I was thinking about modifying my Naim pre-amplifiers. I can now cancel my requests for 10uF/ 25V BC128's...............

I'd kind of forgotten I'd ordered 2 each these:-

Although I did know I had these:-

Much the same as the BC128's I have no idea where these came from, newly put together using SMD components but untested since I've owned them:-

This stock take driven by a request if I had parts to go with the ALWSR's I have. Now I need to put the various parts in to the one spreadsheet.

Regards

Richard

 

[337alant]

Those Mil Spec Tantalum capacitors are brass cased solid tantalums not wet tantalums, different animal in my experience
The wet tantalums have a crimped case at the +ve end.
The Solid tantalums I find have loads of detail but can sound bright and fatiguing IMHO
Not sure why you have an LCR meter for testing Capacitors ??
Alan

 

[337alant]

Where do you plan to use the Teddy regs ??
Alan