What are the obvious visual differences between the two internally?
The DR regs are visually different to the LM monolithic regs by using individual components so the regulator boards look a little busier.
The second is the DR, but isn’t the first one the earlier cb/olive 250?
The main difference internally can be seen around the main transistors which are just under the large black heatsinks in the lower picture above.
Id have said a significant difference is the much larger transformer with the smaller reservoir caps. Plus of course the regulation.
The transformer and reservoir cap sizes are the same with the NAP250.2 and the NAP250DR. You may be thinking of the CB or Olive NAP250.
Ah, i was comparing the picture above.
There are some interesting pics, from different angles, on this 250 pro thread (based on 250-2)
So that suggests the visual difference are the heat sinks? (Unless you look under them)
Not sure, my eyes are going funny looking for differences, not helped by being stuck on a phone, and not being able to categorically know in many cases if a picture is a 250-2 or a DR X)
What we need, is an internal picture of all the 250s to compare. The two we have so far appear to be an olive 250 and a 250dr.
Ah well, I’ll find out in a couple of weeks. Taken a flyer on a reputed DR but I have a niggling doubt. If it is I have a bargain, if not ——-
I have a 250-2 so I will compare the two and take pics when I have it.
Here’s a close up of the heatsink and output transistors on the NAP250DR
On the NAP250.2 they are different (TO NA007s) and the black heatsinking does not have the large bolt holes on top.
Does it have a DR label on the back panel?
Have you checked the service history via the serial number?
Yes and Yes.
I would guess a late olive NAP250?
Note that the NAP250.2/NAP250DR transformer was actually rated at over 1000VA…