Problems with an old Samson Servo200 amp - question about transformer

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Re: Problems with an old Samson Servo200 amp - question about transformer

Post by Folderol »

Also Check electrolytics - especially the big smoothing ones. They should appear short (or nearly so) at first but with a climbing resistance.
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Re: Problems with an old Samson Servo200 amp - question about transformer

Post by ef37a »

You have had some bad luck there RionZ but also some excellent advice.

Warning to all! NEVER connect a moving coil tweeter directly to an amplifier to test it! Always have a capacitor in the path, 1 or 2.2uF electrolytic will do for test, must be non-polar or foil of course for normal operation.

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Re: Problems with an old Samson Servo200 amp - question about transformer

Post by RionZ »

Not been easy trying to source a transformer with the right specs.... this is the closest I can find: https://www.aliexpress.com/item/4001175590204.html?gps-id=pcStoreJustForYou&scm=1007.23125.137358.0&scm_id=1007.23125.137358.0&scm-url=1007.23125.137358.0&pvid=32932b47-1324-452e-b1ce-4a63e0ee3400&spm=a2g0o.store_pc_home.smartJustForYou_925926001.0

Description is a bit vague about ampage, in fact quite a fun read with all the dodgy translation!

Even so, I'm unconvinced I wouldn't be wasting my money... Something must have caused the transformer to go wrong in the first place, and like I said the amp has had very little use, plus surely the fuse should have blown BEFORE any damage was caused... so the only other conclusion is that at a rubbish transformer in the first place - and so replacing it with another rubbish transformer seems a bit mad - especially since the transformer will cost me about 70 EUROS including delivery and I could easily pick up a used working amp of the same spec on ebay for that money.

Looks like it will end up a box of spare parts after-all. And maybe I'll save my pennies and get a Crown, Mackie, or similar.
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Re: Problems with an old Samson Servo200 amp - question about transformer

Post by James Perrett »

If you find an IMG Stageline STA400D or STA800D for a sensible price then snap it up. I've just discovered that they're based on the Hypex Ucd modules which are extremely high quality and you can buy a whole amp for less than the modules cost for the DIY'er. Unfortunately they appear to have been recently discontinued.

Edited to correct the model numbers - JP
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Re: Problems with an old Samson Servo200 amp - question about transformer

Post by RionZ »

James Perrett wrote:If you find an IMG Stageline ST400 or ST800 for a sensible price then snap it up. I've just discovered that they're based on the Hypex Ucd modules which are extremely high quality and you can buy a whole amp for less than the modules cost for the DIY'er. Unfortunately they appear to have been recently discontinued.


Sounds good - I'll keep an eye out, cheers :)
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Re: Problems with an old Samson Servo200 amp - question about transformer

Post by ajay_m »

It's normally quite hard to blow a transformer, other than overheating it. This is a scenario where normally an 'old school' repair-person would connect the unit to a variac and cautiously ramp up the input voltage while monitoring the secondary windings.

One way to test for serious problems is to connect the transformer primary in series with a high wattage incandescent light bulb, such as 100W, which will limit the primary current to a safe value. If the bulb lights up with the secondaries disconnected then, yes, definitely you have a problem such as a shorted turn on the primary.
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