Heraton 345

[Racing]

As has been noted i often base my own builds on old used up tube PA amps.
However,on occasion i dwell on real...different guitar amps too,and i guess Heraton would qualify as such.



So.
Right off the bat,this is really supposed to be a combo amp. DOA though why the seller couldn´t be bothered with the cab,which might as well be just as good as the intent of mine is for a head.



Alright. WTF is a Heraton then? Well. The designer,and owner,of Heraton was a Mr Kurt Rankl down in Bavaria in Germany. From the onset he was the designer,and manufacturer,of amps for Framus. Their "Strato" being their most widespread and known model. However somewhere in the later part of the -60´s that collaboration went sour and Kurt started selling amps under his own name. Heraton.
This at the time when the "horsepower wars" of tubeamps was in full swing why many of the Heratons i´ve seen at least are 4*EL-34 amps of massive power. Not so this 345H though (H for "hall". Reverb in German) which uses a quartett of EL-84´s out back.
None the less Radiomuseum quotes these amps at 50 watts!



Basically i bought this unit for two reasons. Curiosity and the rep they carry. Seing that this unit was DOA it didn´t exactly set me back a fortune so...Said and done.



The whole thing feels rather "german",for lack of better words. Thought through and well executed. As it turns out...not completely without a twist.





*sighs*. WTF can i say? Shippers had a field day,that much is for sure. Nothing a bodyshop hammer and small anvil won´t handle but none the less...*sighs again*



This was rather charming tho! All tubes except one says "Heraton" in bold letters. As for origins your guess is as good as mine. No idea what so ever. Dirty,but that´s handled in a jiffy with some windex and a rag.



...aaaaaand of course DIN jacks out the whazoo... In this case for the onboard reverb.



Guess that doesn´t leave any margin for errror does it?

"It hums".
Yeah. When one of the two screen grid resistors is shot that kind of comes with the territory. Speaking of which that whole deal is kind of Peavey-ish in as much that two powertubes share a common screen grid resistor of 180 Ohms. Seing the 360VDC...weeeeeeeeell..
I replaced them both with 1k ones and done deal,at least for starters.

So. This is a fixed bias amp right. Pot to adjust bias had seen better days no doubt why i replaced it right off the bat. Checked ESR of electrolytes,cleaned the thing out with alcohol from YEARS of nicotine and what not and fired the thing up.
Sure enough. Sound. However real low on power so i took to checking the powertubes on my U-Tracer and sure enough the EL-84´s was about as dead as doornails showing like 25% anode capacity.

Anyways. Tried it out as is and it crackled and what not. As it turns out...the grounding layout of the amp wasn´t all THAT... Chassis "sides" are out of anodized aluminium and see anodizing doesn´t exactly carry galvanic properties.
The speaker out carries ONE wire only,and that is signal. After jumping around like a one legged chicken for a few minutes i discovered that ground of the OT secondary headed for a solderlug that was bolted to one of the through bolts that keep the OT together. Ground is then run via the core of the OT and through the OT bracketry into the chassis side. Well,that didn´t work worth a shit after 40yrs so i opted to just run a wire from the output jack directly to that solderlug and done deal.
Presto.
We now had reasoable sound,albeit real low on power.

Worth noting here is that the amp carries a rather healthy dose of negative feedback but seing that the grounding layout is what it is..that didn´t work all that well either did it?
Hm.

Anyways. Phaseinverter is a concertina in a rather typical German manner. Nothing to write home about i guess.

Then.. Reverb. Replaced the stock tank with an Accutronics one i had laying around. The driver and recovery for this transformer run unit is an ECC-82/12AU7. That and a DIN socket. Replaced that crap with regular RCA ones and let it rip. After some wiggling around...reverb,but only for the one channel though.
Two channels right. One mild and one a little wilder. The wilder ones i´d say,in spite of the concertina setup,carries with it a rather...AC-30-ish vibe. All good IOW.

So.
What´s the general feature of a Heraton 345H then?
Well. Twofold i´d say,for the stocker that is. One is it IS German to the design. What that means is that it weighs in,as a complete running amp chassis,at a mere 7kg. In my book 50 watts and 7kg is a shitload of power vs weight.
Second up..its size. It IS a well designed (well..) very SMALL amp. Does what it claims to and i bet that with a few tweaks tossed at it it´d be a rocknroll amp to count.

[Racing]

Been thinking a bit aaaaaaand... I have to say that i feel that safety,personal safety,leaves something to be desired with this Heraton. True enough,most of what can hurt ya is built into a combo stock but none the less having all that there is exposed to the elements in general as is...nah.
Not only personal safety but from an angle of production as well IMO. Ditto for the fact that the entire amp sports ONE fuse,the mains one.

In turn..that there grounding layout. Amp sports a three prong mains wire alright but what good does that do when the anodized pieces of the chassis doesn´t conduct? Albeit i´ll be cleaning contact surfaces out i´m going to add a positive such. Ie;solderlugs that are physically bolted in place.



For instance. That brings that the ONLY thing providing chassis ground for the OT there is them two M4 screws that keep the transformer in place,and again..as anodized aluminium doesn´t conduct worth a shit... Nah. This needs to be redesigned. It´s that simple.



Ditto in this case. ONLY thing providing ground here is the screws that hold the board to the chassis aaaaaaaaand..again..u guessed it. It bolts to anodized aluminium.



So here´s the solution. As you can see what i´ve done is "countersink" the entire PCB 10mm into the chassis via regular stands. I´m off in a few minutes to pick a couple of pieces of sheetmetal up to cover that there. Just punch the holes needed for the tubes and done deal.

The main smoothing caps has been replaced as you can see,and in turn one has been added. Main reason for that is that there´s an age old adache that tells that we should never load a given e-capacitor with more than two triodes. Hence...
The ECC-82 for the reverb i´m going to hand new tasks in life. Since this amp was produced things has progressed a bit why i´ll use that ECC-82 to power a loop instead.

That aside about every component in sight is fresh.



Uhu. A quartett of JJ´s. Not the sexiest thing around i guess but direly needed,seing how used up the ones in there were.



Yes. The full 9yrds. Thus pots are replaced as well.



Yes. It DOES get a bit clustered but that comes with the territory when working with PCB amps. Actual PCB has been cleaned out as you can see and modified as i saw fit. The copper mask has been cleaned out with some 400grit wet,detergent and water. Made for a hell of a difference.

Nah. We´re getting there alright.

[Racing]

If nothing else i got to install the switched 5V transformer to run the optocouplers..i got to fiddle around with the hardparts for the loop.
Tonecontrol is all done and the small boards holding the H11´s as well.

In short we´re like a few wires away from a,again,running amp. Need to look into that grounding of the OT secondary tho,and for that the OT needs to come out.
I fail to see the reason why one would want all that current running through a piece of aluminium,relying on metal to metal contact,for power? Ie;i will certainly run TWO wires heading directly for the jack and in turn a smaller wire heading for PCB ground. Yes. Albeit the amp will now lack any and all NFB the OT secondary STILL needs ground reference. Key word being reference. In other words no appreciable currents around.



So. This one´s up and running since a few days back. Roaring its heart out. The by Heraton claimed 50 watts might very well be on the mark cause loud enough it certainly is.

Have tossed a few tweaks at it and...getting there. No doubt.



What we´re talking here is a two channel jobbie with a tube powered loop for good measure. Completely controlled by H11 optos in a VERY light package.
Haven´t put in on a scale yet but will later today.

Done though it is not. I still need to install that piece of alu sheetmetal ontop and in turn add a few fuses. Sporting only one mains simply doesn´t do it in my book.

In turn some sort of cab needs to be fabbed for it. Giving thought to using regular plywood in this case. We´ll see where it ends up.

[Racing]

I put the thing on the scale we´ve got at the shop and ya know what....
4,5 kilos!

Then i took to checking maximum AC voltage vs the speakers and ended up with 28VAC into 16 Ohms. Then please be adviced that the OT is specified for 8 Ohms..

Yes ma´m. That´s around the 50 watt mark in the peaks...out of four and a half kilos worth of tube amp.

It has now officially impressed the living daylights out of me. DAMN!!

[ajaxlepinski]

Awesome write up!

I really enjoyed your u-tracer post and this Heraton post is just as interesting.
I plan on watching all your YouTube videos (that are in English)


Where are you going to add the extra fuses?

[Racing]

Thanx.

Extra fuses. One each for each side of the heaters as crossfire and shorts are rather common between for instance plate and heater.
One for B+ voltage,basically for the same reason.

When an amp is tube rectified i usually add one for each HT AC inbound instead and in turn one "saver" diode for each side as well. This to safeguard the powertransformer in the event of rectifier meltdown.

[clipless bumper]

ok - there was a lot in here I didn't understand - but for starters - what are H11 optos and how do they control?

[Racing]

H11F1´s are what´s called optocouplers.

In practice they´re light dependent resistors. Way back such devices you did by combining a lightbulb and a photoresistor for instance in a piece of shrinksleeve (to make sure the photoresistor saw pure "darkness" when the light was off).

These days optos are to be had in regular "cockroach" packages. Ie;the look like any old OP transistor amp or similar.

http://www.vishay.com/docs/83730/h11a1.pdf

Back in the day you wouldn´t run signal through them due to thermal noise and what not,and thus they were mainly used to ground signal for instance. Another such device is the tremolo bug of old Fender amps.

These days tho..tech has come a long way when dealing with optos as with anything else. The feature is,in essence,that they present a REAL vast resistence when "off" and a very minor such when lit.
I use them to actually run signal through them and as long as the datasheet specifications ain´t exceeded it works like a charm.

They want to see a voltage of approx 2-3VDC and their resistence varies a bit with how much voltage. That brings that the H11F1´s i use have a DC resistence of approx 60-70 Ohms when lit and approx 10+M Ohms when turned off.

By implement of these optos in the signal path i get to route the signal to head where i see fit.

That´s the short answer

[Racing]

Yeah,i forgot about that... As you can see a piece of anodized sheet has been added atop the PCB/chassis. Makes for a HELL of a difference as far as structural strength of the unit and what´s more..a major leap forwards as far as personal/electrical safety.

Used the little amp for rehearsals tonight and...altho we play rather crude early metal and hardrock with that particular band this itty bitty tiny thing stood its ground like nobodys business.
In short it´s one formidable powerhouse.

4 and a half kilos worth of powerhouse

All is not gold however. I need to look into it going into self oscillation. If this is due to a bad tube,capacitor or solderjoint of mine..no idea.
At that,due,i´m giving thought to rubber suspending the entire PCB. Simple enough i guess.