Favorite High Power Output Transistor

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K-Amps writes in post 282
" ESR is relevant to the "delivery" of that storage. All that capacitance is

of little use if it cannot be delivered efficiently. People remove their

40,000uF caps and put in one low ESR 10,000uf Blackgate for the

same reason.

Hi K-Amps ,
A guy in our town sells old caps removed from various instruments , I am

attaching a picture of some caps which I got from him , one type is

SIEMENS 10,000MFD100v , and the other is FELSIC CO

4700MFD100v , these are screw type caps and are working ok , they

should be low ESR types I think , he has 6 of these semens and 16 of

filsic that with the siemens I can get 30,000MFD per rail , and with fislec

co I can get 40,000MFD per rail , but the size of both these caps is quite

big , I have another 10,000Mfd 80v cap in the picture to show the size

difference . Do you recomend my using these caps OR I should call

small ones like the 10k80v in the picture but 100v working , also let me

know if 30,000MFD & 40,000Mfd are enough or should I add some

more caps . I do not have any problem of space in my chasis as the

main boards will be mounted on the heatsink only ,
 

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The brand of the other one is Sic Safco, from France, Felsic is the type.

If the Siemens Sikorels are still good, they are the absolute best.
The one you posted is around $40 a piece new.
People overhere would feel very lucky finding those, up till 63V is relatively easy to get, 10.000uF/100V are more difficult to buy.
The Sikorel is from 1991, especially with those capacitors you will have to reform the caps very slowly, Rajeev.

Sikorels have an extreem long life span, if none of the Siemens capacitors are damaged, i'd go for the Siemens.
(sic safco are very good ones too, though)
 
Yes I like the Siemens too. I would check it with a cap meter though, sometimes those big dents can cut away the inner insulations..... **BAM**

I would not use the 80v cap on more than 75v rails regardless.

I do not know the ESR of any of them... but general rule of thumb, newer/ smaller caps have less ESR.. but again there are exceptions.
 
Thanks ,
I too was thinking that these old caps would be better than the smaller cheap caps , I have decided to keep both as I will be making four amps finally for my sound system and these would suffise for two amps,
you did not mention that the MFD would be sufficent or not ? will the storage in these be better in these caps , they are all good , yes some dents are there , also I will slow charge them with a resistor in series for 12 hours and discharge them before use ,

I have taken a picture of how I will be mounting the pcb on the heatsinks , like this I can blow air with a four inch fan , also mount devices directly on the heatsinks , both heatsinks will be V+ and V- rails , I will use no mica washers , I will insulate the heatsinks from the chasis , there will be two sets of these in the amp .
 

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If you have any recomendations for me please let me know , as now I am in the final stages of compleating the amp , the same had got deleyed as I had drifted my interests to the Zeta amp , and I also made eight subbass horns , but now I will compleate this first .
 
Rajeev,

It looks very nice. I like the mini heatsinks you made for the TO-92/ TO-220 devices. The PCB looks like a manufactured board from a Jap manufacturer (albeit from the 60's 🙂 )

For a 400 watts (8 ohm) amp, 20,000uF to 40,000uF per channel per rail is ok. So for a Stereo amp, you have 80mF to 160 mf. You wmight need a softstart pwer up with these. (or as I used to do, a 250 to 500 watt halogen lamp in series with the primary of the transformer later shorted with a relay or second switch depending how high tech you want to go... this solution is inexpensive, and works nicely for a large class-AB power amp. 🙂
 
Vivek,
Yes these coil winding machines are still availible and quite cheap too , around Rs 2500/ 3500 ( less than 100USD )

Jacco & K-Amps ,
Could you guys help out to purchase used , one or two shure SM58 wireless microphones for me ( from ebay or someother place ) I have relatives in the Uk & the US who could pay you and send the material to me ,

K-Amps ,
I am glad you like my pcb , doesent matter if it looks of the type made in 1960s , I am happy , so long this class AB amp gives respectable performance as compared with other pro amps class H of today , and the same is serviceable at my end . I will be making it stereo and it should be around 850watt 4ohms , and 1500watt at 2ohms usable power for contineous 4 to 5 hour pro sound duty in Indian conditions ( in summer the day temp is above 40 digrees )
 
sajti said:



The drivers are run with 30mA class A (single emitter resistor, and 330nF paralell), there was predrivers (BC546B/556B), with 6mA class A. I prefer triple darlington configuration.
The crossover distortion cancelled with about 10mA bias. But I found that the sound is bit sharp. I started to increase the bias, and sound was smoother at about 100mA/device.
I don't understand it, so I measured the B of the MJEs. It starts to fall rapidly under 100mA. It's true for 15030/31, and 32/33. The 34/35 is flat down to 10mA (but I can't get them in my country). This bias looks too much, but for 30W amplifier it means just 3 - 3.5W dissipation for each device...

sajti


I had the same experience with 15028/29 and 30/31 years ago. The had terribly low beta when measured with a standard transistor tester but did ok at higher current. What is so special / strange about these buggers?
 
The really experienced designers like the MJE15XXXX because of what you said, the hfe is very stable even at high current drains. This enables the designer to compensate for the gain yet achieve stable results over a wide range of real world operating conditions.
 
K-Amps
I did not understand your writing ,
"I 'd do what you do, i.e. look at ebay and look at the seller's credentials. Not sure what value I can add since you kow what you want already. " What do you do ??

Thanks for the advise regarding adding a hologen lamp in series of the pri of the main tx , I had a resistor in mind ,

so you guys liked the heatsinks I made for to-220 devices , I have been doing this for years , as it can be made at home easily also I am not dependant on a dealer for supply of the same , I like to do as much myself as possible , thats a dirty habbit in me , however I never thought it was something to catch your attention.

Jacco , no I cannot make the receiver , the SM58 wireless comes with its matched reciever , I heard of e-bay from you people , never visited that site , now I will see
 
Rajeev,

overhere the SM58 mic is sold separately or as a set with a receiver.
The receiver is an EC4, UC4, EUT4, the Shure site probably has more/other receiver models.
A complete set here starts at 150 minimum.

Making the coolers yourself like that is very ingenious
(drop me in India or pakistan and i'll only have expensive ideas,K-ster, probably untill i am starved)
 
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