Apt Holman plug-in MC expansion board

Neat !
I've some SMD skill doing repair on some computer cards. I trained myself by using a small SMD soldering kit bought direct from China. Once soldered, you can watch the LED blink...
Here is the Bangood link of the product I used (I did not buy it on Bangood, there are a lot of sellers on Amazon, Aliexpress,Bangood, Ebay, etc...) but you'll have an idea of the kit I talk about... The parts on the right hand side are a real challenge ... You need proper technique to do it.
Diy smd rotating led smd components soldering practice board skill training kit Sale - Banggood.com|Shopping Francais
 
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Thank you for your answer.
Oh yes, I would like to get the files ! and a shop or a list of shop having the connector (my search did not get much, but I live in France) !

I thank you again in advance !
Here's the bulk of files. Includes the gerber files for board fabrication, the Parts List w/Mouser part numbers (my choices, you may use others), spreadsheets to calculate the gain & load resistors appropriate for your cartridge, schematic and a "build notes" text file.
View attachment Apt_MC-v2_files.zip

...I've some SMD skill doing repair on some computer cards. I trained myself by using a small SMD soldering kit bought direct from China...
Did you manage to solder the QFP-44 chip (0.8mm pin-space) on the back side? The Apt card LTC3260 chip is even smaller than that with 0.5mm pin-space, AND ... the ground connection is by under-chip pad which has to be soldered through a hole on the PCB back side (see the photos in the download files). It can be tricky to get soldered properly.
 
Actually, pads on the back are for identification purposes and serve as a ruler. The only chips to solder are at the front. But I've "successfully" soldered parts very fine on a computer board. I cant remember the exact spacing but I know that i was clever enough to buy more than one before making the repair... I'm more than ten years older now, so I wonder if i would be able to do it (the card was so crowded around it with very important component that I handled the hot air tube with fear...And once the faulty part removed, i did the soldering one pin at a time with some time between them.
But I was very happy to have repaired this card. So the reward was good. (and price very low compared to a new Mobo... )
Thank you VERY MUCH for your work and for sharing it !
I know what project I'll do during the summer if the lock down strikes again in France !
Have a bright and sunny day ! Stay safe.
 
I forgot to tell you that if you want to train yourself to very hard SMD soldering, get a ruined disk drive electronic interface, and remove the integrated circuits, clean the pads with a damp sponge and then solder them back...
These are challenging !
The one I'm looking at has a circuit with 38 pins per side, those pins occupying 14 mm of printed board.. That's a challenge I think... ;-)
 
Hello Seanc,
I spent the afternoon soldering one of your boards (I bought the printed board at the same place you bought yours and used your design. We spoke about that some months ago).
I had problem soldering the SMD parts by hand because you have designed the pads for the components without too much extra space for the soldering iron (I do not know the English term for that). So it was more challenging that what i envisioned ....
So if other people want to test your design, you'd better either change the printed circuit board design if hand soldering or use the stencil/paste and oven approach. Method I could not use because I did not order the stencil with the boards...

Now, I've to devise a way to test the board on the bench because I do not own (for now) the lo output MC cart to feed it... And this is also a challenge because my power supply is dead.
Anyway, it was fun to do it ! Thank you for sharing the design !
Oh, I forgot to ask how you calculate the values of C27/C28 if they are needed ? i did not find anything except they are used for carts needing gain below 10.
 
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George - it wasn't designed to be hand-soldered. Sean designed it to be as high-performance as possible, within the bounds of DIY SMD soldering, which is certainly possible with the solder mask, or by careful application of solder paste, then using the hot pan method.
Having said that, I found the really tiny chip very difficult the first time around, and damaged it with too much heat. The second time around it soldered perfectly, but I used a hot air solder gun instead, after all other components were soldered to the board - it gave me more control.
Hopefully you are able to test it soon, and find it working perfectly.
Cheers,
Greg
 
I had problem soldering the SMD parts by hand because you have designed the pads for the components without too much extra space for the soldering iron (I do not know the English term for that). So it was more challenging that what i envisioned ....
So if other people want to test your design, you'd better either change the printed circuit board design if hand soldering or use the stencil/paste and oven approach. Method I could not use because I did not order the stencil with the boards...
Well, I did warn you it was challenging :), but glad you got it done. The LTC chip is not suited to hand soldering, and I didn't, used stencil & hot plate as described in post #16.

The board design is what it is. I have no need for another, but if I DID do it again, it would be even less suited to hand soldering.

OTOH, the first design was all thru-hole, but required the extra wire for power.

Oh, I forgot to ask how you calculate the values of C27/C28 if they are needed ? i did not find anything except they are used for carts needing gain below 10.
The AD797 data sheet describes the values.
 
Well, I did warn you it was challenging , but glad you got it done. The LTC chip is not suited to hand soldering, and I didn't, used stencil & hot plate as described in post #16.
Oh, boy, yes, it was challenging ! But I managed to solder two of them. As it took me months between the time I read the thread for the first time and now, I did not remember your warning (and I did not remember it either when I ordered the boards... )
And as I borrowed all LR6 batteries in the house I could make a 9V battery using a spare coupler I had. Adding the 9V battery from the scale in the bathroom, I managed to get 16 V to test the boards. I get +/- 12.7V at C15/C17 so the LTC chip is running. I measure the voltages when properly fed with the 18V.
As you can see in the pictures, i can't multiply by two the amount i read in the BOM when I order parts. So the extra board will have to wait for another order from Mouser or Farnell to be completed..... I'm sometimes quite dumb. :scratch2:
Thanks a lot for your design and help, Seanc ! it was really fun to make ! And I plan to buy a LOMC cart to test it in real.

img_2038.jpg


img_2037.jpg
 
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I plan to buy a "cheap" MC cart at first to test the plug-in.
The two possible contestant are two Audio Technica (OC9-XEB or At-F2). Both have an output of 0.32 mV. If I compare to all the carts I own which are around 5mV output I guess I need around 15 gain. So I aimed at this figure... (20 Ohm /316 Ohm).
Experiment will show if I'm right or wrong...
Main problem will be the selection of the capacitance and input resistance... Audio Technica says "above 100 pF" for the capacitance, so I'm good with the 100 pF installed but nothing about resistance...
 
Hello All !
Here I am again !
It took me time (don't ask why) to get an MC cart. Today, I've got one on my desk. It is an Akai PC-200 (a rebadged AT-30E).
The output is a tad lower (0.28mV) so I have to increase gain. No problem with that, but I would like to know what are the safe values for this (min/max)
I was told that input capacitance is non relevant on these kind of cart. But I would like to get your advice on that.
As per input impedance, a local Guru says that I should use about 10 times the coils resistance value... How would you measure non destructively these values ? (I own conventional multi-meters, tube VOM (RCA WV-98C) and a bunch of Chinese made multi-meters including the ubiquitous Chinese transistor tester ?
Thanks a lot in advance for your help !
 
I bought this years ago from a former APT dealer, who had it on the shelf.

There were 3 versions made, not sure if the gain was different or the loading was different. The model I have is 1-A, for 68-70 db of gain with 0.3mv output carts.

Was never able to find a schematic, but all discrete components. Transistors are all Motorola. MPS 4355, 2N 3906, and cant quite make out the other 1.

here are a few pics.
There is a guy on the US east coast that repairs the preamps, he advertises on ebay. He used to work at Apt so may have access to a schematic.

Best
 

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Hi,

No, I'm not a moderator.

Sean designed the boards with my input. He and I built the first through-hole version and the first SMD version, and then georgesgiralt built an SMD board. I built 3 of the SMD boards and they are all in my 3 Apt Holman preamps now (the one TH version I built is in a box).

I also have one bare TH board left, but haven't had more SMD boards made because the interest level seemed to be low. It is possible I might have another batch made, but have to check the BOM for any parts that may have become unavailable in the intervening few years. If you want to pursue this, PM me please.

Cheers,

Greg