ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Hi all,
Got my hands on a old BM4400 (2417) which looks like it has been mangled by a uncaring repairman.
Several of the output transistors have been replaced some by Philips BDV64B some by ST BDV65B and a few ST BDV64B
Not in any particular symetrical way...
I havn't turned it on yet, going to check the trimmers as per standard.. but im worried...
Are these correct replacement parts for the originals, and in this absurd mixed fashion?
all the repairs are sloppy on this one,,, so i anticipate problems...
thanks
//g
BM 2000 *1974, 2x BM 1200, BM 1001, BG 1200, BG CD X, BC9500,BM3300,Bcord 3300, BG CD3300, Beovox Cona, Beovox CX100, Beovox 1200, Beovox RL60.2
A photo of the inside and a few words about what is where, would help us help you.
Martin
Ofcourse, time ran out on me yesterday with schematics and datasheets trying to figure out what has happend here before, and tell the story of this BM
First pic is from left (A) in the schema going towards K in the right direction
So from the schema A ; IC203, IC202, IC201, IC200, IC103, IC102, IC101, IC100
Notice that two caps have been changed here, C147 and C247 has also been replaced (but C247 has been switched to a 470uF Cap instead of the subscribed 100uF which C147 has correctly been replaced with)
There is as can be seen a perhaps stringent application of heatsink paste
As the pics are a bit hard to read here they are from left to right in pic:
ST BDV65B, ST BDV65B, Phlilips BDV64B, ST BDV64B, TIP 141 (original), TIP 141 (original), TIP 145 (original), ST BDV64B
So 64 being PNP and 65 being NPN (TIP 141 being NPN and TIP145/6 being PNP) it seems to check out?
I don't have access to a variable AC, so perhaps just leave it totally unplugged , turn it on and measure the trimmers. .. see what happens, and probe around...
So a few more pics.... turned it on in its naked state,, one trimmer was way off about 37mv (measured across one resistor) the other was ok, both are realy in bad shape, and and wandering a bit with temp, and hard to get exact, but them approx at 6mv
5TR2 the BC142 gets realy hot,.. i know its supposed to as it has a little cooling sink, but im not sure.... it radiates a lot of heat at no load..
So powerlight switches on...
So i plugged headphones in.. without an arial in, i got FM reception,music!
Sliders were oxidized ofcourse... presents work, tuning lights work, signal strenght indicator and indicator lights work..
no idea about the inputs, and as I read from Beolovers writup on this sucker, there are a lot of possible issues lurking in the phono preamp stage..
More to come on thisone...
I did a BM 4400 back in 2012 I think, here the thread (a long one) today it is playing every day, yours look nearly as bad mine did, so get ready for a long haul, good luck
Collecting Vintage B&O is not a hobby, its a lifestyle.
Thanks Sören (sorry my swedish keybord lack danish finesse on the o)
Quite an undertaking, like Beolover's dito, as I lack scope and signal generator realigning of FM boards is rather something i wish to say away from if can be avoided, ..also did you rethread the radio tuner..?
You answered my question on the heat produced by TR2... in any case, im in no hurry, so i will aproach this with caution and study....start with a PM to Dillen on some caps and hopefully a acrylic preset cover :=) mine is ofcourse missing....
A strange item is also that you seem to have RCA connectors in your input stage, must be a newver revision, as they are lacking on mine, not even cutouts in the metal... i though the only variant was the one ending with 01 (with the black front) .