Meridian 101B / 105 monoblocs

[Bushbaby]

Hi All
I made a very stupid error when we moved into our current house in 2003 when I sold my 101/103D pre and power amp for a low and stupid price. I've now managed to pick up as a very good price a 101B and the model up to what I had the 105 power amp(s). The seller for the 101B (these were bough from 2 different suppliers) indicated that he could not test this as he had nothing to use it with hence it went for a very low price. The 105 were indicated as fully working but the external cases do need a good level of restoration being scratched (no dents).

I have undertaken some research on the web, it appears that these do seem to be quite robust with users indicating that they are still operational some 40 years from purchase. I am wondering if I shall just give them a trial with some of my "older" spare gear such as speakers before either putting them into full use or arranging for some sort of refurb (I don't think it will be me to do it)!

Does anyone have an thoughts to moving this forward - this is a system I've always wanted to own long before I was married and that was 43 years ago!.

Best Regards

Rob

PS - I'll add some pics when I've unpacked the power amp as it only arrived this afternoon.

[ppppenguin]

If nothing else run the power amplifiers into a dummy load and measure any DC offset before risking any speakers.

[Bushbaby]

I still haven't had an opportunity to test these but I thought I would give you an interesting update. I Have been in contact with an online "expert" who works on these particular manufactured items for refurbishment, repairs etc. I contacted him to enquire about potential recapping etc and I received a response this morning. It was indicated that it would be £195 for the 101B pre-amp and £215 for each mono power amps (x 2) which would be in the region of £625. I paid £125 for the pre amp and £350 for the power amps so the refurbishment cost will be more expensive than the purchase!
I do feel that I should go ahead and trial these (thanks for your input Jeffrey). I have read on other audio forums that these little units are reasonably robust and unless they are not working or have crackles or such in use, they should be ok to use without touching them. I do believe I'd rather go along this path first.

Best Regards

Rob

[joebog1]

What Jeffrey said. I NEVER connect an old sand amp directly to speakers. If there is some offset it can easily damage voice coils.
If its got shorted output devices your speakers are dead. It will apply 55 volts positive or negative to your speakers.
The circuit is a pretty basic one of a DC coupled amplifier, and any leakage or weak resistors/capacitors in the early stages could be catastrophic.

The manual is here:
https://elektrotanya.com/meridian_105_hi...nload.html

There is a special setup for the power supplies for testing these amps.

Maybe Im out of school, but the quoted costs of a refurb seem a bit high to me. I dont know, Im not in the UK.

Best of luck

Joe

[Murphyv310]

Hi
Let's look at this with a clear mind. If these have been sitting for years even running into a dummy load is not ideal. A leaky capacitor early on will most likely destroy semiconductors even in the output. The charges are far from excessive, how much does an electrician, plumber, garage charge per hour, have you seen the increase in costs of quality capacitors these days? This work is now specialised and for me I no longer do jobs for peanuts. I now take a minimum deposit of £50 and if the client moans I tell them to get lost. TV and Radio engineers unfortunately have had a very raw deal over the years and now most charge a price that reflects the hours worked and time taken to source parts. We are all having to pay up more for everything.

[Murphyv310]

Hi.
I'd also agree with Joe as it is quite a basic design. The thermal switch is......well..... Interesting! Basically a crowbar between the supplies to the early stages, how crude is that! There is a lot that could change value and
If the offset was high then yes a catastrophic disaster could occur.

[Mark Hennessy]

I don't see a problem with the thermal cutout mechanism. The supplies are only +/-10V, so bringing them down to zero does no harm beyond increasing power dissipation in R21 and R23 (from 1.125 to 1.68 watts). Given that the thermal switch is only a single NO pole, how else would you have done it?

Yes, it would have been better to have included an output relay that was released by the thermal cutout - and that would allow the addition of a DC offset protection mechanism to protect speakers from a faulty amp. But such things were almost never seen in UK designed hi-fi amps throughout the 70s and 80s. A shame, but the designers I know cite penny-pinching accountants - all too common in the UK in my experience. In fairness, it is awkward to find a suitable relay with the requisite DC current breaking rating and a high voltage coil - as such, you end up needing an additional winding on the transformer, or wasting heat in dropper resistors, so you can understand the temptation to drop it. Remember, woofers were much, much cheaper back then in real terms. There is an output fuse, which is far from perfect, but much better than nothing.

As audio amps go, this is actually a relatively complicated design - not sure why people are so quick to say it's basic. Meridian did some innovative designs over the years - both technically as well as aesthetically.

As for re-capping costs, this amp only appears to have 5 electrolytic caps (assuming a chunky pair in the PSU). I agree that service engineers are generally undervalued, but this is hi-fi, where many enthusiasts think nothing of paying hundreds for "upgraded" mains cables! Of course, if this chap is popular, the price might be set to manage demand and perhaps exclude a certain type of customer - can't blame him for that!

[Murphyv310]

Hi
I certainly agree Mark re accountants, I was thinking on the same wavelength as yourself re an output relay. The fuse in the output is helpful but the time delay could also mean that a speaker could be damaged. I do have a confession though of accidentally connecting a massive speaker cabinet to the mains which housed two 18 inch woofers plus mid and tweeters. It was connected to the safeblock with a 5 amp Fuse. The bang was deafening, the fuse fortunately blew and believe it or not no damage was done to the speakers.
I would imagine these amps will have a really good frequency response and very low distortion. What does the PSU consist of capacitor wise as I don't see it in the linked diagram?

[Bushbaby]

I will take some inter pics shortly to show what the interiors are like.
I am not going to send these on for recaps etc as £625 is way too much as far as I am concerned especially as it may be just one or two components could be an issue.
As far as I know these are still seen, even 40+ years on, as very good amplification. Hence when the opportunity arose, I just could not resist buying them.

Best Regards

Rob

[joebog1]

OK,
I admit that I dont take on many service jobs anymore. I have a small selected clientele that I DO do work for. They are payers and dont quibble. After all "if it aint buggered, I dont change it ".
Most of the stuff I do is valved, but sometimes a furfy hybrid will sneak in. Its all band equipment, very little Hi-Fi.
I also dont do sand at all anymore, today it really IS complex with all the protection circuits requiring twice the components and complexity of the amp they protect.

When I said a simple design, it almost has the look of an application note from Motorola. The way the output stage is lined up for maximum current gain just looks like them for me.
The BC series transistors gives away the English part of the design. With decent components and a reasonably careful driver, they would sound OK, and would last for years.
The fact that they already have says that.

So when I repair stuff, I mostly charge in Australias currency. That is cartons of beer :-). ( One cartoon is $80, so you dont get many on the pension )
After all I am trying to unload most of my crap as I am starting to get into the fairly high numbers with age.
Valves that cost me fairly large amounts I at least try recover that, but passives I usually give away.

Thats just my take.

Joe