Audio Tubes
Tube Information
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aa - hu
Code Month Year
A January 1946
aa May 1935
aä September 1967
ää November 1943
ab April 1931
ac January 1949
ad July 1944
ae April 1932
af February 1949
ag May 1932
ah July 1947
ai May 1931
ak June 1932
al June 1935
am April 1936
an 1935
ao March 1949
ap January 1945
aq 1955
ar 1939
as February 1955
at March
au June 1931
av April 1961
aw May
ax June
ay July 1967
az August
--------------------------------------------------------------------------------
B February 1946
ba April 1955
bb October 1967
bc May 1955
bd October 1946
be 1952
bf June 1955
bg July 1961
bh August
bi September
bk May 1944
bl November 1967
bm December
bn Same as uq
bp Same as dq
br May 1941
bs April 1959
bt November 1952
bu October 1959
by December 1952
bz Same as zq
--------------------------------------------------------------------------------
ca July 1955
cb October 1949
cc August 1955
cd September
ce 1933
cf January 1930
cg 1936
ch December 1949
ci October 1961
ck June 1944
cl November 1949
cm 1961
cn December
co July 1933
cp February 1930
cq January 1968
cr May 1946
cs August 1933
ct February 1941
cu 1968
cv March
cw 1930
cy October 1940
cz April 1941
--------------------------------------------------------------------------------
da February 1931
db October 1955
dc November
dd January 1962
de July 1930
df February 1936
dg September 1930
dh December 1955
di February 1962
dk April 1938
dl March 1962
dm January 1931
dn March 1931
do April 1968
dp May 1968
dq June
dr September 1939
ds Same as sp
dt July 1936
du August 1930
dw August 1947
dx Same as xp
dz Not registered
--------------------------------------------------------------------------------
ea January 1956
eb August 1953
ec February 1956
ed March
ee April 1962
ef May
eg June
eh July 1968
ei February 1934
ek November 1930
el October 1936
em November 1953
en January 1934
eo August 1968
eö March 1934
ep February 1945
eq September 1968
er October 1930
es December
et September 1947
ez December 1953
--------------------------------------------------------------------------------
fa January 1953
fb April 1956
fc January 1954
fd May 1956
fe June
ff August 1946
fg July 1962
fh March 1940
fi August 1962
fk April 1944
fl September 1962
fm February 1953
fn October 1968
fo February 1939
fp 1954
fq November 1968
fr December
fu July 1942
fv October 1944
fw March 1954
fx 1953
fy February 1942
fz September 1941
--------------------------------------------------------------------------------
ga April 1950
gb October 1951
gc July 1956
gd August 1944
ge 1956
gf September
gg October 1962
gh November
gi December gl January 1957 gm May 1950
go October 1947
gr June 1950
gt April 1945
gu January 1938
gy December 1951
gz November
--------------------------------------------------------------------------------
ha October 1956
hb November
hc July 1950
hd October 1938
he November 1933
hf July 1946
hg October 1933
hh December 1956
hi June 1939
hk August 1950
hl January 1963
hm February
hn March
hr December 1933
hu September 1950
ia - rz
Code Month Year
ia July 1937
ib April 1933
ic May 1936
id June 1933
ie January 1957
if April 1953
ig February 1957
ih March
ii May 1940
ik April 1937
il 1963
im May 1953
in 1933
io 1963
ip April 1939
iq June 1963
it November 1947
iu February 1943
iv June 1953
iy January 1943
iz November 1942
--------------------------------------------------------------------------------
ka January 1944
kä April 1943
kb January 1960
kc April 1954
kd December 1946
ke February 1937
kf September 1940
kg November 1937
kh February 1950
ki April 1957
kk October 1941
kl December 1932
km October 1942
kn May 1957
ko November 1932
kp May 1954
kq June 1957
kr April 1942
ks July 1963
kt August
ku October 1932
kü March 1943
kv May 1939
kw June 1954
kx September 1963
ky March 1950
kz November 1940
--------------------------------------------------------------------------------
l November 1945
la March 1944
lb July 1957
lc August
ld September
le February 1933
lf October 1963
lg November
lh December
ln March 1933
lr June 1946
lt January 1933
lx November 1939
--------------------------------------------------------------------------------
ma October 1957
mb November 1941
mc January 1951
md November 1957
me March 1932
mf August 1942
mg April 1947
mh December 1957
mi January 1932
mk April 1940
ml January 1964
mm February 1951
mn 1932
mo 1964
mp March
mv November 1944
mw June 1938
my March 1951
mz June 1942
--------------------------------------------------------------------------------
na February 1944
nb January 1958
nc February
nd March 1936
ne 1958
nf April 1964
ng May
nh June
nn July 1939
no June 1930
np July 1934
nq Same as bu
nr April 1946
ns August 1965
nu October 1948
nx Same as xu
nz Same as zu
--------------------------------------------------------------------------------
o October 1945
oa May 1930
ob August 1939
oc April 1958
od May 1958
oe December 1934
of 1947
og June 1958
oh July 1964
oi January 1941
ok February 1938
ol August 1964
om March 1941
on June 1930
oo December 1941
op September 1964
or November 1934
os Same as so
ot October 1934
ou April 1930
oz Not registered
--------------------------------------------------------------------------------
pa October 1939
pb July 1958
pc August 1958
pd September
pe October 1964
pf November
pg May 1947
ph December 1964
pl August 1934
pn July 1934
po August 1936
pp Same as dd
pq Same as bd
pr September 1934
ps Same as sd
pt June 1940
pu Same as nd
px Same as xd
pz Same as zd
--------------------------------------------------------------------------------
qa October 1958
qb November
qc December
qd January 1965
qe February 1965
qf March
ql 1947
qn Same as ub
qo Same as ob
qp Same as db
qq Same as bb
qr February 1947
qs Same as sb
qu Same as nb
qx Same as xb
qz January 1947
--------------------------------------------------------------------------------
R March 1946
r September 1945
ra January 1948
rb 1959
rc February
rd September 1944
re 1932
rf 1936
rg October 1950
rh November
ri August 1937
rk 1941
rl March 1959
rm April 1965
rn December 1950
ro May 1965
rp March 1945
rq June 1965
rr July 1932
rs August
ru November 1938
rw February 1948
rx March
rz January 1942
sa - zz
Code Month Year
sa April 1952
sb 1959
sc May
sd June
se November 1935
sf May 1937
sg 1952
sh July 1965
si January 1940
sk December 1935
sl September 1948
sm August
sn August 1965
so July 1948
sp October 1935
sq September 1965
ss March 1937
st December 1938
su March 1938
sx Not used
sy June 1952
sz Not registered
--------------------------------------------------------------------------------
ta August 1935
tb 1940
tc 1931
td July 1953
te 1931
tf 1959
tg June 1947
th August 1959
ti September
tk October 1965
tl September 1935
tm August 1953
tn September 1931
to November 1965
tp December
tq June 1941
tr July 1935
tw September 1963
--------------------------------------------------------------------------------
ua November 1948
ub October 1959
uc November
ud December 1959
ue January 1966
uf June 1952
ug December 1931
uh November
ui July 1943
uk August
ul September 1938
um March 1942
un October 1948
uo December 1948
up February 1966
uq March 1966
ur August 1952
us March 1938
uu Same as nn
üü December 1943
uv 1944
uw September 1952
ux Not registered
uy July 1941
uz October 1931
--------------------------------------------------------------------------------
va April 1949
vb January 1952
vc July 1954
vd February 1940
ve January 1960
vf February
vg March
vh June 1936
vi April 1966
vk June 1949
vl May 1966
vm February 1952
vn June 1966
vp August 1954
vr May 1949
vs March 1939
vt 1952
vw September 1954
vz November 1936
--------------------------------------------------------------------------------
wa September 1937
wb May 1938
wc April 1960
wd May
we December 1939
wf August 1938
wg August 1951
wh July
wi June 1937
wk April 1948
wl June 1960
wm September 1951
wn July 1966
wo December 1937
wp May 1948
wq August 1966
wr September
wt June 1948
--------------------------------------------------------------------------------
xa May 1934
xb July 1936
xc October 1954
xd July 1960
xe April 1934
xf September 1946
xg August 1960
xh June 1934
xi September 1960
xk October 1966
xl November
xm December
xn Same as ux
xp November 1954
xr June 1940
xs Not used
xu Not registered
xw December 1954
xz Not registered
--------------------------------------------------------------------------------
y August 1945
ya October 1960
yb November
yc December
yd September 1949
ye February 1935
yf January 1967
yg February
yh March
yi May 1942
ym August 1949
yn March 1935
yq December 1940
ys January 1935
yt July 1949
yy September 1942
--------------------------------------------------------------------------------
z December 1945
zä June 1943
zb January 1961
zc February 1961
zd Not registered
ze March 1961
zf April 1967
zm May
zn June 1967
zo Same as oz
zp Same as dz
zö May 1943
zq Not registered
zs Same as sz
zu October 1943
zw May 1951
zx Same as xz
zz December 1942
Code Tube Type-Factory-Date-Internal Number.
1.2.3.4.5.6.7.8
-----------------
B 6 2 0 5 7 2 6 ECC82 Berlin 1975.7.26 26
B 5 0 0 8 9 2 8 EF80 Berlin 1968.9.5 28
U 8 1 0 8 9 0 2 EF86 Ulm 1958.9.18 2
U 9 1 1 4 0 0 6 EF86 Ulm 1964.10.19 6
U 3 2 1 0 1 1 0 EF86 Ulm 1970.11.23 10
B 3 1 0 8 6 0 2 EF183 Berlin 1958.6.13 2
B 2 1 1 9 0 0 4 EL12 Berlin 1959.10.12 4
B 3 0 1 8 0 0 6 EL84 Berlin 1968.10.3 6
U 2 0 0 1 1 0 4 EL156 Ulm 1961.1.2 4
U 1 0 0 1 3 0 7 EL156 Ulm 1971.3.1 7
B 0 3 0 1 8 3 0 PC88 Berlin 1971.8.30 30
B 0 3 0 9 9 3 0 PCF82 Berlin 1969.9.30 30
B 9 2 1 0 1 2 9 PCL84 Berlin 1970.11.29 29
B 4 1 0 3 3 2 0 PCL86 Berlin 1963.3.14 20
B 0 3 0 8 8 2 3 PCL86 Berlin 1968.8.30 23
B 1 2 1 6 1 4 6 PL36 Berlin 1976.11.21 46
B 4 2 0 5 6 4 0 PL500 Berlin 1975.6.24 40
B 5 1 0 1 2 0 3 PL508 Berlin 1961.2.15 3
U 8 1 1 5 0 3 7 PY88 Ulm 1975.10.18 37
U 4 0 0 2 1 1 0 UCH42 Ulm 1962.1.4 10
U 1 2 1 8 1 0 6 UF41 Ulm 1958.11.21 6
U 7 2 0 1 9 0 4 XM1000 Ulm 1971.9.27 4
U 9 0 0 3 7 0 1 ZZ1040 Ulm 1963.7.9 1
U 4 0 0 2 4 0 1 6211 Ulm 1962.4.4 1
U 9 0 0 4 7 0 0 D ED8000 Ulm 1974.7.9 00D
U 5 2 0 4 3 0 0 D ECF8070 Ulm 1974.3.25 00D
U 2 1 1 4 0 0 0 J EL8000 Ulm 1974.10.12 00J
Code Tube Type-Factory-Date-Internal Number.
1. 2. 3. 4.5.6.7.8
example: U8116006Z
Factory: U = Ulm; B = Berlin
Day = reverse the 1st & 2nd digit = 18th day
Month = 3rd & 5th digit = 10 or October
4th digit = Last digit of year (1958-1978) decade needs to be determined by construction so, 1966 or 1976 depending on inner construction clues.
The mystery number < > between the rhombus between the pins:
example <5> or <23/6> sometimes the numbers are a mirror image or reversed or backwards - if you hold the numbers up to a mirror the proper direction will be revealed! 79 may be 62 reversed!
The diamond number is the production run and the number signifies the actual person or employee at the time who supervised that glass mold production line. If there was any defect in that run, the tube could be traced back to the supervisor who conducted quality control QC. It means little to be the same number from tube to tube, as we match tubes by electronic measurements.
The "W" signifies "Low-Noise". We see this in American tubes too, the W is the symbol for low-noise. Ruggedized USA Military Spec 12AT7-W for example These tubes, like all tubes with the "W" in the suffix have to meet certain Military Spec standards for shock, vibration, cathode tolerance, longevity with heater life. The "W" suffix makes the this version a smart choice where micro phonics, low-noise, and tube-life are of concern.
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