tandberg-tuner 3001 vs. 3001a


michael <tonihormoni@...>
 

here in the forum are a handful owners of the Tandberg tuner 3001, as
I suspect.

some informations about it:

originally the device had the name (TPT) "3001", above the serial No.
700 the name did change to "3001A". the 3001 had a silver case, the
3001A came into a black case. a "cross-over"-design like the
3001/3001A-tuner, seen this week in ebay (black front-plate, rest of
the case silver), I did never see before.

the Tandberg gets rather warm at the power supply. therefore by all
appearance Tandberg experimented with the design for the ventilation
("chimney-effect"), so that there were two variants of the the upper
lid of the (3001A) case (see also: http://www.nrhf.no/nrhf-TR.html ).

in the course of the production series altogether 7 modification steps
appeared at the tuner, and not two, how the switch of the items name
from "3001" to "3001A" suggest. nevertheless the change of the name
is justified, because above serial No. 700 new boards were used for
decoder and limiter (the decoder-design: easily modified; the
limiter-design: strongly modified, in particular what concerns the
transistor-design).


the modifications in detail*:

(A) circuit: tuning system 1

above SN 400:
- R946 changed from 12k to 4k7
- R948 and R951 changed from 220 Ohms to 1k8
- R931 disconnected from P1001, pin 3, and connected to U906, pin 6

above SN 600:
- R940 changed from 10k to 18k
- R936 changed from 2k7 to 5k6
- CR911 replaced by a strap
- R938 changed from 60 Ohms to potm. 2k5

(B) circuit: tuning system 2

above SN 400:
- Pin11 at U1003 disconnected from R1017 and U1004, pin11, and
connected to ground

above SN 550:
- R1007 changed from 820k to 220k


( C) circuit: main board

above SN 500:
- Potm. 752 changed from 1M to 6M8
- R401 changed from 10k to 33k
- R405 changed from 47k to 100k
- R406 changed from 47k to 33k
- R408 changed from 3k3 to 2k7
- R426 changed from 1k5 to 1k
- R427 changed from 15k to 33k
- R739 changed from 2k7 to 3k9
- R732 changed from 33k to 27k

above SN 850:
- Q401/402/403/404 changed from Siemens to Motorola


( D) decoder:

above SN 400:
- Q504 changed from BC559B to BC490B


above SN 900:
- Q605/606 changed from Siemems to Motorola
- check that C530 is 68pF with U504 from Motorola, and 82pF when using
U504 from SGS

( E) limiter: modified circuit board, above SN 700

( F) selectivity: modified circuit board, above SN 700

( G) power:

CR808 and CR812, 6.8V, changed from Siemens type to Motorola (cause:
inaccurate zener voltage)

(* see also: tandberg-service manual, p. 35)

---


for DIYers

who would like to restore himself should take hold into the eyes an
exchange of the caps C627 and C628 (only drop of bitterness: the
available height amounts about 21 mm merely. therefore you can use
only standard caps - i.e. from black gate - but not the higher grade
types from the same manufacturer).
you also could replace the 5 cement-resitors in the power supply
against MOX types.

On my tuner I have found only one deviation from the schematics-diagram:
C501 should be - according to the diagram - a 22uF/35V Elna-type; on
my item it's a 47uF/35V Elna-Cap.


for a good 3001-item there are – on the long run - known only three
problems:
- the heat (he always must stand "free")
- the contacts from the bridge between decoder and output; you must
clean and de-oxidize them in an interval from 4 or 5 years
- and finally the presets: these must be replaced approximately every
10 years as it is known

by the way I don't know how many Tandbergs were build.
It would interest me therefore whether one owner in this forum has a
model with a SN above 1000? My own tandberg 3001 is a very early item
and has the SN "00042".

best regards - mikel

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