Are EL86 and PL84 the same tube?
Willy Krogstad
Could I substitute EL86 (6CW5) with PL84 if I rearrange the filament system?
They seem very similar according to my Philips 1972 Pocketbook, and they
also look very similar.
The reason for asking is that here in Norway the P-type tubes are very much
cheaper than E-type tubes. Why is constant-current series heater tubes
(almost?) non-existing in audio amplifier circuits? It seems to me to be
very easy to make 300mA cc filament power using LM317 regulators. Is the
6.3V parallell type tubes "religion" or what?
Are the PL, PCL, PCC and so on type tubes worthless?
:-)
Willy
Ron Kremer
<willy.k...@levanger.mail.telia.com> wrote:
>Hi!
>
>Could I substitute EL86 (6CW5) with PL84 if I rearrange the filament system?
>They seem very similar according to my Philips 1972 Pocketbook, and they
>also look very similar.
>
The PL84 is identical to the EL86 except for the filament.
>The reason for asking is that here in Norway the P-type tubes are very much
>cheaper than E-type tubes.
That's the rule everywhere to my opinion. I use a lot of TV tubes
(P-tubes) in audio circuits as they are very cheap to buy and you
nearly always will get NOS made by the famous manufacturers of the
past.
>Why is constant-current series heater tubes
>(almost?) non-existing in audio amplifier circuits? It seems to me to be
>very easy to make 300mA cc filament power using LM317 regulators.
You don't need DC on the filament of P tubes. You can use parallel
feed but have to make dedicated power transformers for that purpose.
DC may be a nice solution in preamp stages as with P-tubes you wil get
the same hum- risks as with E tubes.
Using a LM317 for a series supply configuration is rather risky as
they needto be 'lifted'and their internal protection doesn't wordk
anymore in that case. A slippery measuring pin can mean disaster for
the LM317.
When using P tubes in a heater string arrangement you should take care
that nowhere in the string the maximum permissible Ucath.-filament
value is exceeded. These values are dependent on the tube tube and as
a rule of thumb you have to place output tubes on the 'hot' side of
the string as these have the strongest filament-cathode insulation.
>Are the PL, PCL, PCC and so on type tubes worthless?
They are in many cases as usefull as E-tubes (a PCC88 is similar to
the far more common ECC88 / 6DJ8 but much cheaper to get)
regards Ron
--
Ron Kremer
rkr...@worldonline.nl
'Strive for perfection in everything you do' (Henry Royce)
Duncan Munro
<willy.k...@levanger.mail.telia.com> wrote:
> [...]
>The reason for asking is that here in Norway the P-type tubes are very much
>cheaper than E-type tubes. Why is constant-current series heater tubes
>(almost?) non-existing in audio amplifier circuits?
The P type tubes (300mA) were used in TV's which did not use a mains
transformer. Certainly in the UK at one time, almost all B+W and
Colour TV's were like this. The filaments would all be strung
together and run right off the mains, maybe with a dropper resistor to
get the voltage right.
You probably know the TV background anyway, but why are they almost
non existent in audio amps? For audio purposes, you have to bear in
mind that the filaments near the top of the series filament chain have
large amounts of 50/60Hz AC on them, which increases the amount of hum
injected into the amp.
However, there's no reason why you can't parallel up some PL84
filaments, and run off 15V AC instead of 6.3V - this would be an
effective solution if PL84's are available at low cost.
If you need further data on these tubes to make comparisons, try:
http://www.duncanamps.com/tubedata/search.mv?PL84
http://www.duncanamps.com/tubedata/search.mv?EL86
Always worth double checking, as the ratings on the "P" series tubes
can vary a little from the "E" series relatives...
--
Duncan Munro BOF #23
http://www.duncanamps.com
Brad Thompson
Willy Krogstad wrote:
> Hi!
>
> Could I substitute EL86 (6CW5) with PL84 if I rearrange the filament system?
> They seem very similar according to my Philips 1972 Pocketbook, and they
> also look very similar.
>
> The reason for asking is that here in Norway the P-type tubes are very much
> cheaper than E-type tubes. Why is constant-current series heater tubes
> (almost?) non-existing in audio amplifier circuits? It seems to me to be
> very easy to make 300mA cc filament power using LM317 regulators. Is the
> 6.3V parallell type tubes "religion" or what?
>
> Are the PL, PCL, PCC and so on type tubes worthless?
Willy wrote:
Could I substitute EL86 (6CW5) with PL84 if I
rearrange the filament system?
They seem very similar according to my Philips 1972
Pocketbook, and they
also look very similar.
The reason for asking is that here in Norway the
P-type tubes are very much
cheaper than E-type tubes. Why is constant-current
series heater tubes
(almost?) non-existing in audio amplifier circuits? It
seems to me to be
very easy to make 300mA cc filament power using
LM317 regulators. Is the
6.3V parallell type tubes "religion" or what?
Are the PL, PCL, PCC and so on type tubes
worthless?
*******
Hello--
Not at all-- in fact, too many builders overlook inexpensive TV-type
tubes because of odd heater voltages. The oddball tubes are
likely to be in good supply for some time to come-- unless unimaginative
owners discard them as "useless". In the meantime, you can purchase
these tubes at attractive prices.
Although these transformer assemblies are uneconomical to ship to
Europe, here's a way of heating just about any assortment of
higher-voltage tubes:
FS: NOS Multi-output toroidal xfmr. ass'y. (ideal for heating arrays of
inexpensive odd-voltage sweep tubes). Selectable primary voltages:
100, 120, 240 VAC via switchable fuse panel. Includes EMI filter
with MOV transient protection; built on three-sided subchassis.
Note: you can series-connect windings 1,3 and 4 for use as 119V/1A isolation
xfmr-- troubleshoot those AA5s in safety!
Measured Output Voltages (from four isolated wdgs.):
Output 1: 17 VAC, 4A nominal
Output 2: 22 VAC, 4A nominal
Output 3: 60 VAC, 1A nominal
Output 4: 80 VAC, 1A nominal
(Inquire for more info, incl. test data; asking $9.95 each plus
postage for approx. 12 pounds when packaged for shipment).
73,
Brad AA1IP
Brad Thompson
P.O. Box 307
202 Whitaker Rd.
Meriden, NH 03770-0307 U.S.A.
voice: (603) 469-3351
fax: (603) 469-3917
e-mail: brad.t...@valley.net
DustyChi
0055
andrzej
In Poland only - in tube TV receivers times - be PL841 = equivalent EL84
for paralell filament. ZoltAn
Daniel J. Marshall
>
> Hi!
>
> Could I substitute EL86 (6CW5) with PL84 if I rearrange the filament system?
> They seem very similar according to my Philips 1972 Pocketbook, and they
> also look very similar.
>
> The reason for asking is that here in Norway the P-type tubes are very much
> cheaper than E-type tubes. Why is constant-current series heater tubes
> (almost?) non-existing in audio amplifier circuits? It seems to me to be
> very easy to make 300mA cc filament power using LM317 regulators. Is the
> 6.3V parallell type tubes "religion" or what?
>
> Are the PL, PCL, PCC and so on type tubes worthless?
>
>
> Willy
Hi,
EL86s come up on ebay quite frequently and generally don't even get a
bid. I once bought four like-new Telefunkens there for just over ten
bucks and ten JAN EL86s another time for ten bucks. So, they are quite
ease to come by and are quite inexpensive.
Dan Marshall
Willy Krogstad
"Daniel J. Marshall" <danma...@worldnet.att.net> wrote :
> EL86s come up on ebay quite frequently and generally don't even get a
> bid. I once bought four like-new Telefunkens there for just over ten
> bucks and ten JAN EL86s another time for ten bucks. So, they are quite
> ease to come by and are quite inexpensive.
>
> Dan Marshall
I have some Siemens EL86 and am not sure if I'm going to use them in any amp
anytime - I have got upon myself a GREAT hobby: collecting vacuum tubes! :-)
It's strange - I LIKE tubes! I like reading about them, like to look at
them, and everything with tubes in it has become very interesting... Now I
am reding everything I find about tube amplifiers (have been following RAT
for more than a year) and have almost finished a stereo pp 6CK4 amp.
Is there any system/order with the E and P tubes? Or maybe it's 'quite by
luck' the EL86 and PL84 are the same tube only with different heater system?
(I really need some decent tube data books!)
And: Thanks to everybody who replied to my question both in RAT and by
private email!
-Willy
Nick Sheldon
E series and P series valves are very similar in most but not all cases. The
real difference is that as the P series were intended for TV use (no
filament transformer - instead, a large wattage dropper resistor which got
*very* hot), they are of little value in repairing hi-fi unless one does
something of a rebuild. The consequence of this is that they have almost no
secondhand value, and are extremely cheap even when new (the PCL86 is 25p
each here in the UK in quantities of 1000+).
I use P series valves in both new hi-fi and new computers, and have received
extremely good comments. On a watts dissipation per pound/dollar basis, it
is very hard to beat the PCL86.
Nick Sheldon
Willy Krogstad wrote in message ...
Franz Hamberger
Willy Krogstad <willy.k...@levanger.mail.telia.com> schrieb in im
Newsbeitrag: rvC75.1239$Dxe.18...@news.telia.no...
Hi Willy,
> Could I substitute EL86 (6CW5) with PL84 if I rearrange the filament
system?
> They seem very similar according to my Philips 1972 Pocketbook, and
they
> also look very similar.
Yes, the EL86 is a PL84 construction with 6.3V heater.
Since there was already an EL84, they had to use a new
designator.
> The reason for asking is that here in Norway the P-type tubes are very
much
> cheaper than E-type tubes. Why is constant-current series heater tubes
> (almost?) non-existing in audio amplifier circuits? It seems to me to
be
> very easy to make 300mA cc filament power using LM317 regulators. Is
the
> 6.3V parallell type tubes "religion" or what?
Using an LM317 as a 300mA current regulator is the optimal solution
to heat the P series tubes when used in audio amplifiers.
It's not recommended to connect a series heater string to a
higher AC voltage, because of hum introduced by the
heater-cathode leakage current.
I usually provide a 24 to 28 volts DC supply and limit the
current by an LM317 for each heater string.
So the most P type tubes can be used with a single heater
voltage.
> Are the PL, PCL, PCC and so on type tubes worthless?
No, if you use them right they are as good as the E types,
and you save a lot of money. I got lots of P tubes on
fleamarkets nearly for free.
An excellent audio tube is the PCF802, for example.
For small amplifiers PCL86 are excellent, even the
PCL85 can be used with success. I tried it myself.
And don't forget the easily available PY88, two of them
make an excellent full-wave rectifier with warm-up delay
to avoid high transient plate-supply voltages.
So enjoy what you have got and don't support greedy
tube dealers who want to sell you their expen$ive
'high-end' tubes.
Franz
--
Franz Hamberger, Berlin, Germany, franz.h...@gmx.de
My Online European Tube Charts - Tubes & Valves Database
http://people.freenet.de/radiolabor/index.html and
http://www.ginko.de/user/franz.hamberger/index.html#tubes