lm741 which is most suitable

[intensate]

Hi I have a Wem copicat ic300 and its has 4 741 in it ,all the same .
They are SFC 2741dc 7821.
There are many different types and wonder which would be the best replacements?

Thanks

 

[JonSnell Electronic]

I would fit another 741.
RS Components | Industrial, electronic products & solutions

 

[Mooly]

If you are trying to upgrade them or just want a play then try something like the OP134. I would also add a small 10uF 50v standard electrolytic cap across pins 7 and 4 for a bit of close decoupling.

 

[turk 182]

is the unit working?
if it is don't change the spec on the devices used.

 

[intensate]

turk182
The unit is partially working I can hear the incoming audio but the echo does nothing

 

[turk 182]

change the tape loop and check record bias....tape heads ok? all guides correct?...man it's been long since i played with tape loop stuff...

 

[intensate]

tape heads

do these look ok?

 

[turk 182]

can i see the emulsion side of the tape loop please?


and a different view of that erase head, left side please.


do you own a frequency counter? and are the heads showing signs of magnetization?

 

[intensate]

tape heads

tape

 

[turk 182]

dude you need to find a reel of 1/4 inch tape, a splice block and some suitable splice tape first.


i have a suspicion that homebrew connection from the erase head to chassis is not correct....

 

[intensate]

Thanks every one
Turk 182 someone has been in it before me,whats wrong with the erase head?

 

[turk 182]

without a schematic in front of me and from all the one's i've seen i've never seen that erase head ground tied to the chasssis.


has someone changed or updated the power cord?

 

[Mooly]

http://wem-owners.com/wp-content/uploads/2015/07/ic300.jpeg

 

[turk 182]

thanks Mooly! i guess it would not matter as both the erase an PB heads are common to case.( it just looks wonky)


up next would be confirming the 40khz bias oscillator is functioning(i wonder if anyone monkied with the bias trap filter?)

 

[intensate]

schematic

thanks

 

[Mooly]

up next would be confirming the 40khz bias oscillator is functioning(i wonder if anyone monkied with the bias trap filter?)

I was thinking that too, osc working or not... that 8.5 volts across the 15uF cap on the osc supply would be a good place to start particularly if the op hasn't a scope.

 

[Mooly]

... in fact all the supplies should be checked. First rule of fault-finding and all that.

 

[intensate]

I have a scope with a frequency counter

 

[turk 182]

....i always thought that the first rule was "never test AC with your tongue like you would a 9v battery!"


oops i better stop typing and stay with scotch....for awhile...

 

[intensate]

I am running it through a dim bulb and a variac