Stanley Labs SL106B Frequency Counter

[andrewn]

Does anyone have any information on this instrument? This one is dead. It has been modified by the previous owner to use an external battery pack which I think was made up of 8 size F (huge!) nicads. I had to dispose of that many years ago because it was leaking with several duff cells. If I hook it up to 9.6v it only draws 21mA with nothing on the display. When plugged in to the mains, the green power light illuminates and 20V is available (for charging) on the battery lead but that's it. I plan to remove some of the pcbs if possible to further investigate.

[David Simpson]

Andrew, I wonder if Stanley are a well known make. I put out a post a few months back (25th April) regarding a similar Stanley counter timer - the SL114, but never got a reply. Mine has 3 channels, and three led's denoting KHz, MHz & GHz.
I couldn't find any info on the data sites either, BAMA, Mauritron, etc.

Regards, David

[andrewn]

Hi David, like you I couldn't find any thing on the internet so I would have to presume it wasn't a popular make. Mine says made in UK on the back panel and the constructional quality seems to be good. Most of the components are readily available types so I think its worth repairing. I have found the two LM309 voltage regulators have failed and also a BFY51 transistor on the power board. If I bypass the regulators and supply 5V from an external psu, I get zeros on the display but I can't get it to measure anything so I'm going to have to check the input circuitry now. It would be great to get some data on this instrument such as the frequency range and min/max input level etc. Regards Andrew.

[Alistair D]

It sounds like there could be damage to some of the TTL chips if the 5V rail has failed. The other area worth looking at is the master clock and the dividers that provide the gating pulses.

Al

[David Simpson]

Folks, shall put out a picture of my Stanley SL114, along with three much primative timer/counters. L-R, Venner TSA6334A/2(with a Panax 402ST on top), Advance TC4, then the Stanley. Shall just keep the Venner for nostalga sake.
Pity there isn't any technical info available for the Stanleys.

Regards, David

[andrewn]

Well I seem to have had some success in repairing it. On temporarily fitting a pair of 7805 regulators it seems to work properly. The reason I couldn't get a reading on the meter before is because the input circuitry used the unregulated side of the PSU which I had bypassed on my first experiment. The only problem now is without a battery connected the unregulated voltage is 16V which causes the regulators to get very hot. When the battery is connected the unregulated voltage is 11V. The battery is charged at 0.5A which seems very high for what must have been 1.2Ah nicads. When the power switch is in the charge position the nicads simply charge through a 15R resistor. When the switch is in the mains position, the charge goes through a BFY51 and 2N3055 transistor as well. A pot on the board enables me to adjust a current charge between 400mA to 800mA. As I reduce the charge current, I find the unregulated voltage reduces as well. I would have expected the opposite as there would be less loading on the supply rail. Does anyone know if such a fast charge was typical on equipment of this age? As far as I can see the charge won't shut off by it's self so you would have to be careful not to overcharge. The counter draws 810mA in use so the battery wouldn't have lasted long between charges!
It's not worth me buying nimh cells for it as I have no need to use it on battery power. I was thinking about mounting the regulators on larger heatsinks in the area where the battery would have been fitted.
Regards, Andrew.

[Alistair D]

It certainly sounds odd that the unregulated voltage falls with lower charging current. Wht about replacing the batteries with 3x 3V9 5W Zeners or I have 22 and 27R 50W metalclads here and you are welcome to 1(p&p only). The resistor could be mounted to somewhere on the metalwork.

Al

[Herald1360]

In the professional models of NiCd 1.2AH was subC, C was around 2AH and D, 4AH. 400mA is fine for permanent charging of the D size cell and 800mA wouldn't matter too much for equipment used for a few hours at a time.

Cheap consumer varieties, though, generallly were 1.2AH for both C and D sizes. The weight was a giveaway.

[andrewn]

Originally Posted by Alistair D

Wht about replacing the batteries with 3x 3V9 5W Zeners or I have 22 and 27R 50W metalclads here and you are welcome to 1(p&p only).

Hi Al, I think I'll give it a try. I've had a look in my stock and I've got some high wattage resistors but thanks for the offer.

Originally Posted by Herald1360

In the professional models of NiCd 1.2AH was subC, C was around 2AH and D, 4AH. 400mA is fine for permanent charging of the D size cell and 800mA wouldn't matter too much for equipment used for a few hours at a time.

I hadn't considered it might have been fitted with D size cells. It seems likely given the high current the unit draws and I think eight of them would fit in the space.

Regards, Andrew.