Will advise on Bowens Monolite monoblocs

<p style="margin-bottom: 0cm;">Lars, the Bowens Monolite 400 you own is of the very first series of mono bloc flash units ever made by Bowens of London, matter of fact, they claim they are the very first ones to put a compact flash unit on the market in 1968. The Daly capacitors <span lang="en-GB">DALY PSFT X34 63/10/6CW </span> you show are probably at least 31years old and the <span lang="en-GB">electrolyte </span> may have dried up to an extent<span lang="en-GB"> and </span> the <span lang="en-GB">oxide film on the anode aluminium foil may have deteriorated very much, decreasing capacity and increasing the leakage current. However, you can not necessarily deduct from the fact that the pre-charge neon on the Monolite 400 stays on that the capacitors are bad. That symptom is also present in numerous other faults in the control circuitry; replacing the flash capacitors without knowing the true fault may be throwing money out of the window. Therefore, you should have a technician with experience in the repair of flash units take a look at the Monolite to find out what is really wrong. Perhaps it is just the transistor that is sitting next to relay 2 or3? That's a 25 Cent part!</span></p>

<p style="margin-bottom: 0cm;"> </p>

<p style="margin-bottom: 0cm;"><span lang="en-GB">If there is the need to replace capacitors you may have a problem to accommodate them physically. The old ones are 50 mm in diameter and are mounted by a stud, and new ones in  capacitances around 1000 </span> <span lang="en-GB">µF</span> <span lang="en-GB"> will be  38 mm in diameter, and without stud. This calls for adapter plates and spacers to keep them in place securely. </span><br>

<em><span lang="en-GB">"Can I still use the 330V 1000 µF from epcos.de"</span> </em><br>

<span lang="en-GB"><span style="font-style: normal;">I'm afraid not. You need the 350V types at least, or better yet, the 360 V ones. The working voltage of the old Monolite 400 is 640 VDC unregulated, therefore the flash capacitor pack is made up of 2 banks in series connection to be able to operate at that voltage. If capacitors connected in series change their electric properties, especially their capacitance, the imbalance in the set up may drive one or more capacitors into over voltage condition. Using 330 V capacitors in a 640 V series connection set up in an unregulated charging circuit as found in the old Monolites is literally asking for trouble. </span> </span> <span lang="en-GB">When the voltage applied exceeds the insulation capability of the anode foil, liquid electrolyte and the separating paper layer the capacitor will react violently and may explode with a loud bang.</span></p>

<p style="margin-bottom: 0cm;" lang="en-GB"><!-- @page { size: 21cm 29.7cm; margin: 2cm } P { margin-bottom: 0.21cm } --></p>

<p style="margin-bottom: 0cm;" lang="en-GB"><span style="font-family: Times New Roman;"><span style="font-size: small;">Hope this helps</span> </span></p>

<p style="margin-bottom: 0cm;" lang="en-GB"><span style="font-family: Times New Roman;"><span style="font-size: small;">Hans</span> </span></p>

<p style="margin-bottom: 0cm;" lang="en-GB"><span style="font-family: Times New Roman;"><span style="font-size: small;">One last note: </span> </span></p>

<p style="margin-bottom: 0cm;" lang="en-GB"><span style="font-family: Times New Roman;"><span style="font-size: small;">How about closing this thread and opening new ones with more specific titles. Would make manoeuvring easier. Thanks</span> </span></p>

<p style="margin-bottom: 0cm;" lang="en-GB"><span style="font-family: Times New Roman;"><span style="font-size: small;">Hans</span> </span><br>

 </p>

<p>Hi Hans,<br>

I have just bought a Monolite 800E (130$ with a strong Manfrotto stand) without user manual. It strobes at all powers and seem to have not any troubles, but I've some doubts:<br>

1. the READY 'red lamp' always is blinking (initially slow and then gradually stronger, but it never becomes 'fixed red').<br>

2. The botton with 'flash icon' (on the right of control panel) seems to have not an effective ON / OFF role.<br>

Is this normal or signs of looming troublesomes ?<br>

For its maintenance, is it a good idea to sometime repeat your 'capacitors formatting procedure' ?<br>

Its sync connection is by a 'peanut'; can I use instead an inexpensive <a href="http://cgi.ebay.com/Wireless-STUDIO-Flash-RT-16-TRIGGER-4-Receivers-16-CHAN-/130390740507?pt=Camera_Flash_Accessories&hash=item1e5be4ce1b">Wireless STUDIO Flash RT-16 TRIGGER</a><br>

IMPORTANT INFO: If somebody is still looking for a spare flashtube, he can find it here (£ 66 + VAT):<br>

http://www.peartreephotoshop.co.uk/product-p/lu357.htm<br>

All further suggestions or advice would be appreciated.<br>

Thanks for any answer.</p>

<p> </p><div></div>

<p>Hallo Hans,<br>

i have a question?<br>

On my Hensel(same as Bowens Mono) the ac powerjack is broken!<img src="http://s006.radikal.ru/i214/1101/a1/a2fa857dd473.jpg" alt="" width="600" height="440" /></p>

<p>And i want to change it. The question is how do i get there?<br>

Do i need to discharge the flash? Someone told me that I can discharge the Flash by pushing the test flash button immediately after turning the flash down (does it works?)<br>

i saw your photo with open Monolite:<br>

http://static.photo.net/attachments/bboard/009/009d61-19830984.jpg<br>

as i understand to get to the power jack i need to take off , all the back wit all the dials?<br>

i will be deeply grateful!<br>

ich werde Sehr dankbar sein!!!<var> </var><br>

rgds Toms</p>

<p>Hi Toms,<br>

it is not a safe place to go. getting at the back of the chassis involves removing the whole case, annoyingly. you can't just remove the back. Discharging the unit is best done with a large resistor on aligator clips attached to the tube contacts (once removed). but as I said and Hans has pointed out, these are dangerous high-voltage units. I have a habit of leaving the resistor in place across the caps whilst working on a unit.<br>

t</p>

<p>Hi T Feltus,<br>

thanks for your response! I just bought 4700 Ohm resistor, 11 w, and alligator clips! Is it save for a flash tube, to attach a resistor on tube contacts? When I will connect the resistor would I fell or see in some way that the flash is discharging? I have the volt meter but its cat 3 till 250v, can I use this one or the flash is at higher voltage?<br>

brgds, Toms</p>

<p>Hi Toms,<br>

no no, take off the tube. there are two small screws near the modeling light, the reflector and tube assembly comes off, exposing three contacts labelled as "high voltage", so clip the resistor on there (and put the resistor inside a box so you don't touch its wires).<br>

the operating voltage, according to Hans, above, is 640vdc, so i would leave the resistor on for a couple of minutes before checking. The 400 should have a good dump circuit, but it is never worth risking even with a disposable flash.<br>

t</p>

<p>Hi T Feltus , I wonder if I may ask for some help ,During the recent cold spell in the Uk two of my Bowens Monolight 400's became unusable as tempratures fell well into minus .<br>

the units were not used for a month , on use units were swiched on and left to warm with Modelling lamp on ,on switching to flash charge and ready lamp worked fine but unit will not flash by either test button or wireless trigger ,there was no smoke no bang no nothing ,any pointers would be very greatly appreciated ,unit is now totally stripped and nothing found ,are the circuit diagrams available anywhere .<br>

Thanking you Paul.</p>

<p>I might have them for the 800E which is a little different. I have no idea how the cold could have affected the unit however. if the charge light is coming on, then i expect that the caps are charging ok. did you (carefully) measure the voltage at the tube contacts? The first thing to try, I think, is to check tube voltage, then also check the sync voltage to make sure that it is not the trigger circuit that is gone. the sync voltage should be 35VDC.</p>

<p>thanks for the response ,two units gave up ,I assume during this spell as the room they were in became very damp as well ,just decided not to flash ,will try as you say tube voltage etc .one component I assume is suspect is marked RCA 7647 :D3202U and I think feeds a power reg transistor , ah ! it's all coming back to me ,slowly I hope .</p>

<p>Hi,<br />A friend of mine tried to use his studio lights on a diesel generator. Both burned out instantly. <br />One is a Bowens Mono Gold and the other one is a Hensel Compact-B 1000. Both of them have the capacitors from the voltage doubler swollen and leaking.<br />The Bowens capacitor is marked with:<br />STC<br />24uF RED HT<br />350V REVERSIBLE<br />NP 224 350<br />H00 BSS<br />and the Hensel capacitor is marked only with an internal cod: HENSEL SK 3 <br />My problem is that I don't know the values for the Hensel capacitor, but also for the Bowens, everything I found on the market are really small capacitors (meaning dimensions) and I don't think that they are good replacement. <br />Does anybody knows what value the Hensel capacitor is and can you please direct me to a store where I can find these kind of flash capacitors. I've searched the net and I found some stores, but they have only the big (value) capacitors for the main bank.<br />Thank you</p>

<p>Hello Hans!<br>

This initiative of yours is very kind.<br>

I have occasional problems with my Monolite 800E monoblocks. Sometimes one of them just refuses to fire. Manually or with synchro cell or cable, it is the same. It charges, the "ready" light is blinking normally, but it just doesn't fire.<br>

I have this guy that took a look at them and he doesn't know what is wrong. He just resolders some points that seem suspicious to him and the flash works well again ... for some time.<br>

He asked me if I could find a circuit scheme. Can anibody help me finding it somewhere?<br>

Thank you in advance.<br>

Regards from Croatia.</p>

<p>Hi there,<br /> I have a couple of old Bowens 750w Silver monos that I think haven't been used in a while.<br /> What would the formatting process for the capacitors in these be?<br /> I'm thinking the "B" one as the housing is black but am aware this model wasn't specifically mentioned. Could anyone put my mind at rest please...<br /> Thank you</p>

<p>Hi Guys,<br>

Hans seems to have vanished, sadly. And also I have not really got very far with my Bowens units, in fact, I have 4 in a box dismantled.<br>

Aaron, I am not aware of a black 750 existing: the 750 I knew of was one of the older designs, with pressed aluminium caps on the casing... If your black one is like these, I think the design is a lot simpler than the later black ones. Said this, I have two silver 200s that I have not got working, as some of the peculiar proprietary components baffle me.<br>

Dag, I do have a partial schematic, but it is of the 400e, and obviously of the pre-charge component that the 800e does not have, so it is of little use. I never found a full schematic of any of these units.<br>

T</p>

<p>Thank you T Feltus, I have only 800 Ws units.</p>

<p>Hans - thank you for info posted long ago on old Bowens heads. I was about to dump my old bo-lite but thought to look for spare parts and/or info before burial. Nothing to lose I went through a version of the 1/2 second - 1 second - 5 second power up routine and amazingly after 15 mins charge I got a pop on test button. It's not very powerful but the barn doors and grid have made it very useful to me - it has been a key light in many a set-up so deep gratitude to yourself - made my day. Derek Simpson</p>