Some friends of mine, who just do the odd (very) family gig have one of those old, and, mostly reliable Pulsar 2250 sound to light controllers..

The reliability is, I suspect down to the fact that the controller has no controls its just a speaker lead in for the audio, and a bulgin cable out to your screens etc. (oh, and a power lead of course).

However, dispite its very careful storage, and very occasional usage 2 of the channels are now fully on. A classic triac "jammed open" fault.

Does anyone know if lighting controller triacs are generic between controllers? or are there all sorts of wierd and wonderful specifications. I seem to remember someone once telling me that they simply chucked 400volt 1000watt triacs into every controller they owned and repaired themselves, but maybe he was just lucky with his "one size fits all" approach.

The Pulsar unit that they're needing the triacs for offers 750watts per channel.

Anyone know somewhere I can buy a few compatible triacs from?

Cheers

What is the marking on the faulty triac Gary? Or has it partially evaporated?

What little remains of the writing on the triacs surface is unreadable - appears to be only lettering though. No numeric remains.

Are the triacs isolated from the heatsink by means of a mica sheet?, do the triacs share the same heatsink?.

I have plenty of triacs lying around, I can easily send you a couple to try.

Can you see the part number on the triac on a good channel? Is is assuming that it is the correct one in the first place!

providing the pin assignment is correct, (cathode anode gate), voltage rating, current rating, isolated or non-isolated tab and the voltage rating is fine then triacs are interchangeable.

Good luck with the repair.

Cheezy

On a similar note... about triacs...

Does anyone know where I can get some BTA 08-600TW triacs? These are the triacs used in the NJD Euro 4e controllers.

I tried the triacs available at Maplins and they do not switch (BTA08-600B). I've put a meter on the triac pins and there is no switching. The fuse has been replaced on the problem channel and I've even tried two different triacs that I got from Maplins.

I've been to a local disco shop and he won't sell me a triac, but he will repair the unit at what I believe is an unreasonable price... especially when, if I had the part, I could do the repair myself.

I've been in touch with NJD and they want another unreasonable price for one triac and they want to charge a fortune for a courier to deliver it to me! I know electrical components can be delicate, but they won't just put it in a suitable box or jiffy bag!

Many thanks,

DJJ

I did try some research on this topic and I'm guessing that the 'TW' bit at the end of the triac description is important as the Maplin triacs are only described with the 'B'.

I think one of my controllers might be the Pulsar 2250 I will have a look and let you know. I may just be able to see the part number.

Got me here!

You have to take the triac out of the circuit. Does the lamp work with the triac out of circuit? If it does, you have a major short.

Is the fuse after the triac? If there is power there then the circuit is complete and you have a problem post triac. Most likely in Bulgin plugs or socket, these do fail occasionally.

I take it you have checked the triac using a resistance checker when its out of circuit?

If you are able, substitute a working triac as a temporary check of the driver tranny.

I hope it helps. PM me if still stuck.

Regarding the BTA08-600TW Triac.

BT is a code meaning Triac (bi-thyristor). 08 means it is 8 amps. The 'A' means it has an isolated tab so can be bolted straight to an earthed metal point safely. 600 means it has a peak voltage of 600VDC which is a bare minimum for any unit on 240V AC. The T means it's a hyper-sensitive logic-level gate trigger, (ie driven straight from an IC rather than through an optocoupler or pulse transformer.) The W means it's of 'snubberless' construction which means it can switch inductive loads such as motors and transformers without additional safety circuitry.

From memory, Pulsar use the Texas Instruments (TIC) series, NJD use Philips (BT) and Ryger use SGS-Thomson (ST) parts.

So it's not that simple. Get it wrong and it can either half-wave (ie flicker or blow motor windings) or simply not power up. At worst, it can introduce a short from mains to chassis. One letter out can mean all the difference!!

Take care.

K. Edwards

The Euro 4E will accept the following triac without fuss:

Philips BT137X-600D

Available from RS Components, most electrical wholesalers will order for you if you don't have an account.


PS : A Previous post said to observe gate, anode, cathode. I think he was getting confused with thyristors as Triacs have three terminals: MT1, MT2, gate.

Just to re-iterate, some chasers are VERY fussy about the type of triac required.



K. Edwards

Right! I've got the 3 lines of info from one of the other Triacs in the controller.

BTA
08 4005 (could be an S at the end instead of a 5)
85M


My mates looking for 3 of these.

Thats a BTA08 400S. The 85M is a date code (1985) you can ignore that.

Jon.

Yes it is an 'S' at the end. It means it's a sensitive gate type which means very little current is required to fully trigger it.

Regarding BTA08... triacs

The sensitivity suffix from poor to high is as follows:

none or A - low
B - medium
C - high
S - very high
T - logic level

This relates to SGS-Thomson parts only. Different manufacturers use different codes, the BTA series is SGS-Thomson (logo ST at the top of the casing)

For example the Ryger footlight 4 and DX403 uses the TW suffix, logic level with snubberless design. (see my earlier post.)

If a triac is snubberless, it does not require a snubber network. This is additional pcb circuitry hooked across load and switching terminals to ensure the triac stays conducting throughout both halves the mains cycle, and prevents re-triggering when the drive is turned off, known as DV/DV latch up.