Products > Test Equipment
Test Equipment Anonymous (TEA) group therapy thread
factory:
--- Quote from: Vince on March 20, 2023, 10:15:30 pm ---...snip...
As for my QUAD 33/303 pair, it's still not finished I am afraid... I tried to order the trannies and cheap 1 buck 4 pin DIN connectors I need, along with the light bulbs for my Tek 7603 all in on order. No luck. Spent a lot of time checking several sites but no one seller had all of these items, never mind in stock. Resorted to checking Digikey and Mouser, and splash 50 Euros with them... still no luck.
So I am so upset and bored and fed up with this repair taking forever...that I have now got used to the idea of spending 10 Euros of shipping to buy the trannies in one place, the DIN connectors in another place, and give up on getting the bulbs altogether. 2 out of 3 work and the scope is usable as is, so no emergency there, especially since it's not my daily driver.
So yeah, I need to order these freaking trannies and DIN connectors this week if I want to push these amps out the door at long last....
Before I get rid of them I will try playing some music through them just in case I like it. So far I have only tried them with a tone from my sig gen.
--- End quote ---
If it helps I will be ordering from Mouser at some point this week, I'm sure the capacitors I want will be more than enough to exceed the free shipping limit, will probably get a few extra 74LS90 in SOIC too, they are about £2 each.
David
Vince:
That's very nice, would help me indeed ! :-+
For the QUAD 303 power amp I will have x4 2N5322 please :
https://www.mouser.fr/ProductDetail/610-2N5322
They cost an arm, 12+ bucks for these alone, before tax.
Then some Midget grooved light bulbs type #337 for the graticule of the Tek 7603 scope :
https://www.mouser.fr/ProductDetail/560-337
I will have 10 of them, gives a much better price per unit. So that's 5.51 dollars before tax.
So about 17+ bucks for these little things alone, crazy eh ?! :-//
If you give me a bit of time, I would need some specialty things as well... I just had an idea for a project, and I would need R-2R DAC resistor arrays. I don't think it's the kind of thing I would find locally... but mouser probably has some.
I would need one for 8 bits, which I guess must be very common, but also a 9 bit (or more) one, which I am not sure exists.... I bet you can only get these things for 8 bits maximum ?!....
I guess I could take an 8 bit one and add / calculate the required two extra resistors to add the ninth bit, worse case scenario... but an off the shelf one would be easier and tidier, if they exist.
I have never bought these things so if someone knows what search terms to use in the search engine, or have examples of brands or part numbers, I am all ears....
ch_scr:
--- Quote from: Vince on March 21, 2023, 07:43:21 pm ---If you give me a bit of time, I would need some specialty thing as well... I just an idea for a project, and I would need R-2R DAC resistor arrays. I don't think it's the kind if thing I would find locally... but mouser probably has some.
I would need one for 8 bits, which I guess must be very common, but also a 9 bit (or more) one, which I am not sure exists.... I bet you can only get these things for 8 bits maximum ?!....
I guess I could take an 8 bit one and add / calculate the required two extra resistors to add the ninth bit, worse case scenario... but an off the shelf one would be easier and tidier, if they exist.
I have never bought these things so if you know what search terms to use in the search engine, or have example of brand or part numbers, I am all ears....
--- End quote ---
Vince, it's called a R / 2R DAC, because there are just 2 values. It get's even better, the second value is just double the first! All you need is a stock of decent quality resistors (like those metal film in the flat blue cardboard box, I also have some, you remember the type?) and you put one and then two in series; to make up your ladder, can go as long as you need! You can make it better, if you sort them, to all have the same value as close as you can get it - no need to buy anything! For 8 - 9bit, it'll be fine, especially if you pick them, to be 0.1% instead of the 1% they would have usually...
Vince:
Yeah sure, but an off the shelf DAC would be much tidier, more compact and turnkey.... and probably very cheap, I assume ?! Has to be... it's just a resistor array...
If they are abnormally expensive or hard to get then yeah, I would have to resort to cobbling one together myself... but it's not the aim, if I can avoid it.... :-\
ch_scr:
--- Quote from: Vince on March 21, 2023, 08:26:46 pm ---Yeah sure, but an off the shelf DAC would be much tidier, more compact and turnkey.... and probably very cheap, I assume ?! Has to be... it's just a resistor array...
If they are abnormally expensive or hard to get then yeah, I would have to resort to cobbling one together myself... but it's not the aim, if I can avoid it.... :-\
--- End quote ---
There should be an 8 bit DAC or two in the stuff I sent you? 5V positive logic this time, I promise!
"Just an resistor" starts to get really expensive, really fast, because it only makes sense, when the performance is better then "just doing it yourself" with "cheap" 0.1% resistors! If one does it with 0805 smd, it's quite small, too. You will find resistor networks most easily with (up to) 8 "uncomitted" same value resistors, than then can be arranged as needed - but stay away from the cheap thick film ones, they have worse long term drift, as all thick films. Such a "proper" network can be easily 5€ a pop - you'd need more than one, naturally. In almost all cases, it would be wasted on an 8 bit DAC, too. In the stuff I sent you, maybe there are some "thick-film, 8 single resistors"-networks, if you insist on that. Buying an off the shelf 8 bit dac will be the cheapest option anyway, but I'm not one to discourage tinkering!
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